Since they don't need to build houses they are great at rushing since the resources and time spent on houses can be diverted to building an army. Their unique unit, the Tarkan, is fast and relatively tough cavalry unit that is great at destroying buildings and archers, making them effective raiders. They have effective cavalry since in addition to Tarkans they can build Paladins for heavy duty combat and Cavalry Archers for quick ranged support. Cavalry Archers are cheaper than normal for the Huns, so they will likely make up a large part of a Hunnic army. Their Trebuchets are more accurate than those of other civilizations, which aids them in destroying enemy buildings or siege weapons from a distance. The Huns' faster stables allow them to replace lost Paladins faster.
Their infantry are weaker as they lack the Plate Mail Armor and Champion upgrades. In addition their siege weapons are somewhat lacking, missing the Onager and Heavy Scorpion upgrades. They are geared purely for offense. They have a pitiful defense that can be easily broken as they lack Guard Tower, Fortified Wall, and Hoardings. As such players should not spend resources on building defensive structures. Instead they should spend them on more units to constantly attack the enemy so they won't have the chance to attack in the first place.
They are short of gunpowder units, having only Cannon Galleons (which is removed in The Forgotten), Petards and Demolition Ships. Such situation would likely put the Huns in great disadvantage in facing a civilization with other gunpowder units. Being unable to research redemption would mean that the Huns can never convert any enemy Bombard Cannon. Being the only Old World civilization missing the Cannon Galleon in the Forgotten expansion is a critical weakness in maps where water is common, as this causes naval invasions to be much more difficult. If an opponent builds a large number of towers near a shore a naval attack is almost impossible.
While the Huns remain viable in the late game, they are generally very predictable as their only strong Imperial Age units are Paladins, Trebuchets and Heavy Cavalry Archers. This lack of flexibility in their army composition can easily put them at a disadvantage.
Huns are easily one of the most dangerous civilizations in the game, but they are also one of the hardest to use right. Due to not needing houses they have a more flexible start, and can boom without worrying about population blocks. They can easily fulfill most early game strategies, but become less versatile in the Imperial Age, so ending the game quickly is important.
Huns can do standard Dark Age rushing (drushing) and Feudal Age rushing (flushing). However, they are at their strongest in the Castle Age. Their cheap and powerful Cavalry Archers make for devastating raiders, with the range of an Archer and speed and durability of a Scout in one package. Due to their cost reduction, Huns can easily flood the opponent with Cavalry Archers and barely lose any. If micromanaged effectively a group of six to ten Cavalry Archers is nearly invincible if the foe is in the start of the Castle Age or end of the Feudal Age. So a the player must watch out for large numbers of Knights though, and keep Spears or Knights handy just in case.
In the Imperial Age, Huns mostly rely on Heavy Cavalry Archers and Paladins. Hunnic Trebuchets are more accurate, making them a good go-to Siege weapon.
The Huns' new unique tech, Marauders, allows them to create Tarkans at the Stable. This synergizes with their team bonus (Stables work 20% faster), meaning that the player can rapidly churn out large numbers of Tarkans.
The cost bonus for their cavalry archers was reduced due to game balance issues. In addition, Treadmill Crane and Cannon Galleon have been removed.
Huns are extremely good in team battles, due to the Cavalry Archers' ability to keep several different foes in check at once, if micromanaged well. They should play in the frontline position, since they are great rushers, and this will help the team keep pressure on the enemy.
An allied Italian player is useful for Huns, because the Condottiero can fill their infantry weakness. The speed of Condottieri allows them to keep up with the cavalry. They are suitable for repelling enemy Halberdiers, and even Camels.
The Hunnic knight line benefits from the Frank and Persian team bonuses. The Mongol team bonus also synergizes nicely, bringing the Light Cavalry more line of sight. This is especially helpful in a combined Cavalry Archer/Light Cavalry rush. The Briton team bonus (20% faster archer range) also aids the Huns' Cavalry Archer production.The Berber team bonus (Genitour available at archery range) is great for the Huns, because it provides them with a fast ranged support unit (also with full set of archer-related techs open for them) that they get at a discount. If allied with them, Hunnic castles can also amass Tarkans and accuracy-enhanced Trebuchets quicker once received Kasbah upgrade.
The Huns' cavalry is considered to be one of the strongest in the game, as they have access to every key technology for their cavalry units (such as the Paladin and Hussar upgrade) except for Camels and Battle Elephants. As such, they have a significant advantage over civilizations that rely on archers (Mayans, Ethiopians, and Britons) and civilization with weaker cavalry (Britons, Koreans, Ethiopians, Byzantines, and Malay), thanks to their team bonus that allows their Stables to upgrade and train their cavalry units faster, and a strong early game economic bonus.
The Huns are one of the few civilizations that can go for a cavalry archer rush, since their cavalry archers are cheaper (other civilizations that can go for such strategy includes the Mongols, Magyars, and the Vietnamese). As such, the Huns can effectively counter slow-moving units such as Champions, the Slavic Boyar, the Persian War Elephant, the Southeast Asian Battle Elephant, the Teutonic Knight, etc. by hit-and-running them.
Being an early game civilization with strong economic bonus (starting at maximum population and not needing to build Houses means the Huns can effectively save a lot of Wood in the early game for an army), combined with their ability to pump out Scout Cavalry and Knights faster, and cheaper Cavalry Archers, means the Huns have an advantage over civilizations with weak early game, such as the Spanish, Portuguese, Turks, Saracens, and Vietnamese (especially in open maps like Arabia and starting in the Dark and Feudal Age).
Having access to more accurate Trebuchets against units and Siege Rams, combined with their unique unit, the Tarkan, the Huns have the capacity to tear down civilizations with incredibly strong defenses in the early Imperial Age, such as the Chinese, Byzantines, and the Teutons (that is until Bombard Cannons and Siege Onagers come into the play).
Having access to fully upgraded Hussars, combined with their access to Heresy and their Stables working faster, means the Huns have an advantage over civilizations with strong Monks, such as the Aztecs, Spanish, and the Burmese.
Since they don't get access to gunpowder (aside from Petards and Demolition Ships), they have a disadvantage to civilizations that get access to it (like Turks, Portuguese and Spanish), especially if the game starts in the Imperial Age - this of course before the game enters into the Trash wars.
The Huns' naval capacity is incredibly lackluster, as they do not have access to Cannon Galleons, Fast Fire Ships, and Shipwright. As such, civilizations with strong navies (such as the Malay, Berber, Portuguese, Vikings, and Koreans) will have a significant advantage over the Huns in water maps (especially in the late Imperial Age when coastal defenses are built).
Because most of the Huns' military consists of cavalry units, civilizations that have access to strong Halberdiers (such as the Goths, Burmese, Japanese, Slavs, Byzantines, and Celts) or unique units that deal bonus damage against cavalry units (such as Italians' Genoese Crossbowman and Incas' Kamayuk) can be problematic for the Huns in the late-game. Similarly, civilizations with strong Camels (such as the Indians, Berbers, Malians, and Saracens) are a threat to the Huns' cavalry in the late game.
Much like the Mongols, facing the Berbers will be a challenge for the Huns, as their Camel Archers and Genitours can easily decimate the Huns' cheaper cavalry archers, Berbers' cheaper Camels that regenerate health can be problematic to the Huns' Paladins and Hussars, and their cheaper Hussars and Berbers' access to Bombard Cannons can decimate the Huns' Siege Rams and Trebuchets. The similar logic can be applied with strong Bombard Cannons (such as the Italians, Turks, Portuguese, and Spanish) in regards to the Huns' Trebuchets and Siege Rams.
Mayans, Incas and Aztecs have Eagle Warriors that can effectively counter their Cavalry Archers (Eagle Warriors deal bonus damage to archers and cavalry at the same time).
Vietnamese Rattan Archers and Imperial Skirmishers can counter the Huns' Cavalry Archer army. Other prominent civilizations with good skirmishers that can also do this are the Aztecs (with the Atlatl technology), Byzantines (their Skirmishers are cheaper) and the Britons (whose Skirmishers are created faster and get +1 range out of Yeomen technology).
The Goths can be a nasty rival to the Huns in the late-game, as their Huskarls and cheaper Halberdiers can counter the Huns' Cavalry Archers and cavalry units respectively. Similarly, the Malian infantry bonus with higher pierce armor makes their Pikemen more threatening to their Huns' main army (Paladins, Hussars, and Cavalry Archers).
Since the Huns' defensive capacity is lackluster and their siege capacity is limited to Siege Rams and Trebuchets, civilizations with strong siege weapons (such as the Ethiopians, Teutons, Celts, and Koreans) can effectively level any of the Huns' defensive structures (especially in closed maps such as Black Forest and Arena).
Despite the Huns having access to one of the strongest late-game units (the Paladin), the Huns' army composition is very limited in the late-game. As such, civilizations with diverse tech trees such as the Byzantines, Malians, and Chinese will have a significant advantage over the Huns in the late-game.
The Huns are incredibly strong wide open maps such as Arabia and Nomad due their strong early game economic bonuses and their strong rushing capacity with their cavalry units.
The Huns are also incredibly strong in 1v1 matches due to the said economic bonuses.
Having their Stables work faster means their ability to train light cavalry faster allows them to deny the relic in Capture the Relic maps.
As their unique technology Atheism halves the cost of Treason in regicide, they have a very distinctive advantage in that game mode, as they must always know the enemy kings' location. Also, Atheism adds +100 years to Wonder and Relic victories, which also gives them an edge in Standard Game matches when a player intends a Wonder/Relic Victory, and the Game mode "Defend the wonder"
They are probably the strongest civilization at Deathmatch games, because as they don't need houses, all three of their starting villagers can be tasked with building military buildings, and their -100 wood penalty is invisible in that game mode while having their population limit on top so they can spam their units non-stop almost as the game starts.