I recommend Karthus if you're feeling like you're hardstuck in low elo

I used to play a lot of karthus a few years ago and climbed to plat basically spamming him mid or top on another account. Just come back to league again after a long break and after feeling like the game is a dumb lottery coinflip keeping me from climbing I am playing him again and I have to say hes great for teaching players about paying attention to the map and whats going on and promoting a careful playstyle of farming and outscaling. I ended up about 100 cs and 3 levels ahead of my lane opponent eventually even though I didn't dominate my lane simply because I was alive and farming gaining gold and exp while he wasnt.