It's not really about who fox loses to, but who he has the most trouble against and how much work he has to put in to earn the matchup. Take melee for example against jigglypuff or samus. It's like, sure a perfect TAS worthy fox has that matchup or it's even, but one mistake can lead to his death, possibly with one grab, especially jigglypuff who capitalizes on mistakes easily. In pm, those characters that give him trouble are samus, mewtwo, puff, sonic, zelda, ROB, G&W, bowser, peach, kirby, ike, roy, and marth... Quite a few characters I must say.