While not every fight in Final Fantasy 16 will be as flashy as the Eikon battles, it is still full of unique bosses who keep players on their toes. While the mission to sneak into the Empire's capital to destroy their Mothercrystal seems crazy enough, things don't go according to plan as the Imperial Cannonier shows up.
This boss is a large man with a massive cannon, fitting for his name, that fights with slow-moving but high-damage attacks. Quickly into the fight, the room will begin to fill with Aether, so be prepared for a second phase.
Imperial Cannonier First Phase
The Imperial Cannonier will be able to counter you close up or from a distance, and despite having three other companions, he'll usually focus his attention on you. With Clive's limited ranged options at this point in the game, it's best to fight him close up and try not to get knocked away. His melee attacks are slow and easy to dodge, usually in either two or three-hit combos.
Try to fight him from his side and wait until he uses some of his longer wind-up attacks to get in a few powerful abilities to wear away his stagger bar. His flamethrower attack can be quite dangerous at a close range. If you see it, continue dodging straight back until it's over. He'll have another attack where he slams his cannon into the ground called Black Powder. As long as you're outside the few circles of effect, this is an excellent time to lay down the hurt.
Bring a few hard-hitting quick abilities, such as Rising Flames and Scarlet Cyclone, as their shorter attack times will allow you to get out of the way before the boss begins to attack again. Attack quickly in these windows without getting greedy until you eventually wear down his stagger bar. While he is staggered, utilize your best abilities and Limit Break to make short work of his first phase.
Imperial Cannonier Second Phase
This second phase is fundamentally the same as the first, as he uses a lot of the same moves, just in stronger forms. He will be much more aggressive and quicker between attacks, making your counter-attack windows even shorter. All of his cannon attacks will fire off more projectiles, so prioritize dodging even more than before.
He also now has the Rocketeer attack, which will launch him across the battlefield. Be sure to chase after him utilizing Phoenix Shift, as he will land and quickly switch to his ranged cannon attacks. He will also have another new attack called Hard Launch, which will leave him open to attacks after landing and is easy to dodge. Save your Limit Break until he is staggered to maximize your damage and finish off the Cannonier for good.