Top 3 entries from some of my MangaDex 10 / 10 lists (based on difference between my rating of 10 and the actual rating), with shitty descriptions:

Completed

A Complicated Sibling Relationship 4-Koma

• rating: 7.79 (difference: 2.21)
• greatest trainwreck I have read

I Guess I Became the Mother of the Great Demon King’s 10 Children in Another World

• rating: 8.16 (difference: 1.84)
• MC pops babies out like nobody’s business to save the world; the kids are cute though

I Decided to Fake a Marriage with My Junior to Shut My Parents Up

• rating: 8.20 (difference: 1.80)
• MC turn lesbian to stay with her roommate

Ongoing

Crossdressing Quest

• rating: 8.12 (difference: 1.88)
• MC awakens to something on his way to save the world

The Magical Girl ♡ In Her 30s

• rating: 8.37 (difference: 1.63)
• title describes itself

The Gals Who Always Say Insane Things: My Daily Life at a Private Paranormal High School

• rating: 8.44 (difference: 1.56)
• gals use superpowers for random BS

Kinda NSFW

Don’t Call Me a Naked Hero in Another World

• rating: 7.09 (difference: 2.91)
• MC gets isekai-ed with only her bath towel

Rosen Garten Saga

• rating: 8.84 (difference: 1.28)
• most sexually deviant manga I’ve read

no third entry due to a lack of 10s