for me, it's Bison Steak. Literally white scrap, but with additional flat +25 HP bonus, which doesn't even matter because you're going to lose that health in a matter of seconds during late game. old Bison steak was also better, as it increased regeneration on kill, however now it is replaced by cautious slug, which can recover all your health pretty fast if you have 3-6 stacks, tougher times or just skill of avoiding damae

i could also mention shield generator, as it disables OSP (one-shot-protection) after getting 2 stacks, and there is already a lunar item that replaces your health with shield, not to mention annoying shield recovery. however, it's not that bad as full shield can remove not one, but 3 eclispe modifiers
saying this as 300 hour player. Feel free to share your thoughts on what is the worst item, and which item is best to scrap/avoid picking up.

Also, beetles have done nothing wrong.