Some more cozy / slice of life power fantasies:

• Bofuri - A scaredy cat signs for an MMO with her friend, and decides to invest all her stats into defense. This unique strategy turns into a game-breaker.
• Slime 300 - After dying from overwork, a young woman is reincarnated into a fantasy world. She vows to take life slow this time. After 300 years of unintentional level grinding, she suddenly finds she is the strongest witch in the world.

Dumb, silly fun power fantasies:

• Classroom for Heroes - Your standard overpowered idiot shonen hero in a magical academy full of waifus. These shows are a dime a dozen, but this is one of the few I actually enjoyed.
• Kemono Michi - A goofy, feelgood isekai where all problems can be solved with wrestling. No real plot, but the cast is fun and has good chemistry.

Power fantasies which take themselves a bit more seriously:

• Gate - A portal opens up in modern day Japan, and a fantasy army invades. The army is immediately routed by modern firearms and tactics, and Japan ends up counter-invading the fantasy world. Attempts to show a realistic first contact scenario, though the writing is sometimes grossly jingoistic and fetishistic.
• So I'm A Spider, So What? - Character is reincarnated as a lowly spider in the world's most dangerous dungeon. Very satisfying to watch them progress from bottom of the food chain to world's strongest monster. There's a whole second half of the plot involving more conventional isekai'd highschoolers, but it's much less interesting and can probably be skipped.