Some characters work well in 1 vs. 1 others not so much. Some characters will be a bad match for others while for some characters they won't be. The important thing to remember is when DLC is added the characters are balanced/ made with FFA in mind not 1 vs 1. Normally in a FFA game at least one other player will brake the mine and this leaves Isaac wide open and not enough time to plant another. It's cool people play 1 vs 1 with this game don't get me wrong but it'll never be a fair fight as this game isn't built for it.