Master Yi was one of the first champions ever released for League of Legends way back in 2009. In recent years he has gotten to be quite underpowered compared to the rest of the field, however, so he was often looked down upon by many players as not worth using. Master Yi died too quickly and just didn't do enough damage. This lack of utilization led Riot Games to completely rework Master Yi recently. After the recent overhaul, he is actually worth using now.