Reaching the maximum floor of your company and getting the final reward.
When kidnapped by her own father, Lisa instructs Cody to find bombs and blow up his tower.
Blowing up Dr. Disc's tower in the first game, floor by floor.
After Dr. Zero defeated Prince Tail's father, the King attacked him and left him for dead. Zero repaired his original body with cybernetics, and when he returns, he calls out Prince Tail for what the King did.
Dr. Zero's revenge on Tail Kingdom and Porombo Island; he confronts Prince Tail with the truth of his past and defeats him, becoming the Legend1. Zero uses his newfound power to take over the castle, its soldiers, and the entire island. When Tail then loses to Cody, Zero imprisons Princess Darcy in a mirror, strips the Prince of the Legend3 title, and dismisses them both. His revenge is so complete that in the sequel, he solely focuses on killing Cody since he already got his revenge on the Royal Family.
Defeating Prince Tail's Draco robot, which is one of the hardest fights in the entire game.
Defeating Dr. Zero's Brute, which knows the game-breaking Alpha moves.
Defeating Hunter's Golden Sunny to free Darcy.
A lot of Cody's time travel shenanigans result in obtaining XStones from impossible places, like a sealed volcano or an alien.