Most Toxic Feature?

Of all the mechanics in this game what do you think is the most unhealthy to the game? Not a specific character skill (cough, YASUO WIND WALL cough) but an overall mechanic that affects multiple champions.

For me its undoubtedly invisibility. The idea that you cannot see an attack coming unless you've placed an item down (which you can only carry one of at a time) or have switched to scanner (which has a CD) makes it an incredibly hard to deal with feature. Couple this with escapes the many of these characters have, their burst potential, and it creates interactions that are not fun or competitive, but more a "This character appears, deletes another character, then disappears" loop.

How to fix it? Maybe something like an afterimage, where you see artifacts of where the champ was as they move so you can have a vague idea of where to try and land you skillshots. Or up the amount of pinks you can carry, something like that.

To me it's about counterplay. Tanks can (usually) be kited. Assassins can be CC'd and burst down. etc. But invisibility is a mechanic that is less about a 1v1 skill gap, and more a gimmick that requires you to spend gold and play cautious because the opponent has an advantage you cannot overcome through skill alone.

SO!

What about you? What's a game mechanic you think is toxic, unbalanced, or otherwise?