Here is the full list of all 21 Roy Cluse: Itsy-Bitsy Edition achievements.
Collect 50 martinis.
Collect 50 bottlecaps.
Collect 50 blood bags.
Feast on 50 other spiders.
Travel an accumulated 10,000 feet.
Unlock Will of the Ancients skin.
Unlock Ash skin.
Die from falling 25 times.
Unlock Bubblegum skin.
Die from brambles 25 times.
Die from flytraps 15 times.
Unlock Blue skin.
Unlock Purple Boi skin.
Jump 200 times.
Unlock Mrs. Roy Cluse skin.
Use your dash attack and land in brambles.
Avoid death with the bloodbag 10 times in one playthrough.
Collect all Roy Cluse skins.
Collect 100 gems in one playthrough.
Unlock Duke skin.
Unlock Green Machine skin.