Here is the full list of all 11 Titanis achievements.
Beat the Game.
Beat every mission in the game.
Find a secret area.
Kill 500 Enemies.
Buy all the weapon upgrades.
Buy all the boot upgrades.
Beat the giant Motocco.
Beat the giant Motocco without taking damage.
Beat Vexx without taking damage.
Loot 2000 gold.
Do 1,000 damage to the practice dummy.