Knuckles VS Rouge
From Sonic Retro
Knuckles and Rouge have one battle at the end of both their parts of the story.
It happens after the Meteor Herd and Mad Space Levels.
They fight over a fenced-in lava pit. To win, you must hurt your opponent enough times. This can be done with power glides, jumps, and punches/kicks. There are walking platforms, but you can also climb the arena to 3 separate levels of the structure in which to do battle.
After the Fight
Regardless of who wins the fight...Rouge and Knuckles reach a standstill. They start arguing, causing Rouge to lose balance and almost fall into the lava. Knuckles saves her, and they both have a brief intimate moment. Rouge then give Knuckles her Master Emerald shards before both go their separate ways.