Here's a couple of examples:
**Dawnchaser Sejuani** has been released with a poorly-made splash art, where her anatomy is straight-up wrong (thin right arm unnaturally bent, misplaced right ear, right boob larger than the left one despite the fact it should have been the opposite because of the perspective) and her face (particularly the lower half of it) can only be described as "fugly". People have been complaining about it for months, but as far as I know Riot doesn't seem to have acknowledged it.
**Pirate Ryze** has been released with an unfinished joke animation. Riot stated they were going to fix it, even though it was complicated. Well, two years have passed and it's still unchanged.