So if you could gift your worse enemy one game and they had to play it from start to finish what would that game be??.

Easy. Space Invaders. It never ends. This is your life now.

E.T. for Atari 2600.

Two great choices

Superman 64

Final Fantasy X, it's my favourite game of all time and I'd happily play it again!

Action 52. It gives them 52 terrible games to play.

999999IN1 with those repetitive games that only change the array colors

Clicker Heroes. It's an idle game that they won't escape unless they click mindlessly for 500+ hours. I'll also demand they get all trophies/achievements that the game has to offer. After that they'd wish they weren't my enemy.

But this game is free, so nothing to gift here. For a paid game, I would give a less frustrating game named Celeste (assist mode deactivated, also need to be completed 100%).

Balan Wonderworld, pure torture.