From Destinypedia, the Destiny wiki
The Colossus is a robust type of Cabal elite warrior.
Massive, even for Cabal standards, they lead through their own relentless demeanor, wielding devastating Gatling-style Heavy Slug Throwers and Cabal Slug Launchers. Colossus also possess radios that allows them to make reports back to their command centers.  They tower over most Cabal infantry with their rapid fire weaponry and near-impenetrable armor, they are the most devastating unit in the Cabal's roster. They are powerful enough that a stomp from them can shake the ground beneath them.
The Colossus is the single most dangerous Cabal unit in the order of battle, clad in nearly impenetrable armor and armed with a devastating arsenal of heavy weapons. Their primary weapon of choice is none other than the Heavy Slug Thrower, a large rotary machine gun which fires a hailstorm of microrockets at an incredibly fast rate. It is also shockingly accurate at long range, rendering any position on the battlefield potentially unfit for cover. Any Guardian who steps in its line of suppressive fire will have their shield melted in the blink of an eye and will be unable to fight back, for the microrockets fired can knock the player's aim off by a significant amount, so it best to stay mobile and run away.
Colossi also have the ability to fire homing missile swarms from pods on the back of their armor. These missiles have a high velocity and blast radius, so dodging them can prove to be a difficult prospect because if a full barrage hits their target they could swiftly destroy the player. Although Colossi dominate at long range, facing them up close is a bad idea as they will unleash a three-hundred-sixty degree ground smash called the "Quake" that can instantly kill Guardians. For those few that survive, they will suffer massive damage and tremendous knockback, causing them to die of impact with a hard surface at sufficient distance.
However, as fearsome as the Colossus is, they can prove to be vulnerable due to their low mobility, despite their ferocious size and strength. Precision weapons are good for taking them out at a distance while fully automatic weapons allow them a quick death up close.
In Destiny 2, Colossi serving the Red Legion primarily wield Cabal Slug Launchers that are capable of rapidly firing slugs or even energy beams. Red Legion Colossi also utilize Cabal Cluster Missiles, which function like a standard Colossus' missile swarm. However, these missiles are fired in larger clusters, deal Arc damage, and have a longer range. If these missiles hit, they will cause the player's screen to glow white for a few seconds, blinding them and greatly reducing their movement speed, effectively having the same effect as a Fallen Web Mine, albeit wearing off faster. Red Legion Colossi also utilize their jetpacks more often than Colossi of other legions.
List of appearances