The Annihilator is available for 150,000 bolts when reaching Tyhrranosis. With use, it can upgrade to the Decimator, which releases heat-seeking mini-rockets once the main rocket explodes on contact. In challenge mode, it can be upgraded to the Mega Decimator from any Gadgetron vendor for 580,000 bolts.
The Annihilator is a long, orange weapon, with several metal parts grafted onto its barrel, and with blue highlights also on its barrel. It launches rockets from its wide nozzle with a good rate of fire. The Decimator is larger and thicker, with three pure metal parts that protrude past the nozzle, as well as on the stock. There are also more blue highlights featured on the weapon.
The Annihilator is, at its core, a simple rocket launcher, with a good rate of fire and solid range. Its damage holds up for the entirety of the game, and is strong against the majority of enemies and bosses once it is acquired. Though it is initially best against single targets, such as medium-to-large enemies, the upgrades adding additional bomblets and mini-missiles upon impact make it greatly useful against both groups and the toughest enemies. Said damage output, range, ammunition capacity, and blast radius makes it a very versatile weapon and useful against all threats throughout the game.
The V2 Annihilator rocket drops scattering bomblets (akin to the Bouncer) upon detonation. At V3, these bomblets home in on enemies. V4 gives it an additional lock-on mod, which makes it easier to use against larger targets. At V5, the rockets release mini-rockets rather than bomblets, which deal even more damage, and can hit flying enemies as well.