yi is the strongest 1v1 champion in the game
he is a melee champion with no cc with a kit designed to 1v1. in order for him to be balanced with the 50% riot aims for for all their champions, due to the nature of mobas riot simply cannot produce a 50% winrate on yi without buffing his kit to a point where he becomes the strongest 1v1 champion
and as a yi man with 1300 games i can tell you. yi is the strongest 1v1 champion in the game. he will beat every champion in a 1v1
but yi does have counters. the counter to yi is the fact that this game is a 5v5, not a 1v1. yi is the strongest 1v1 champion, but he is below average and sometimes useless in a 5v5
for example. champs like zac or maokai with equal gold will provide more to a teamfight than yi. but yi will beat them 1v1
the only other melee champion in the game to my knowledge with zero CC is katarina . but her kit is AoE focused. so she is like the teamfight yi. kat is the Yi that is strong in teamfights but weak in 1v1
next. garen, darius, and mundo are 3 melee champions with "almost no cc". so their 1v1 power is close to yi. but yi still defeats them 1v1. garen/darius/mundo have overloaded kits due to being melee champions with "almost no cc".
now as for yi tactics. i am a yi god in toplane and i can destroy any champion 1v1 including riven, jax, irelia, darius, anything
would take me a minute to wrote out a little guide. if you want me to write it for you i can