Why are you calling out Butterbean like that? It's not his fault he's big boned.
Well... "have wing chunners ever won against other styles?" yes. I would guess at some point in time the stars aligned and a wingchunner was successful in a fight. that and also maybe some fat kid took up boxing and got mauled by a very athletic counterpart of wingchun.
Traditional forms, regardless of where they come from, regardless of how ancient or how tricky, can never keep up in terms of combat practicality than styles that are used for competition, and that's a lot of the issue with Wing Chun. There are guys who do Wing Chun who are great competitors and who are serious fighters, both in Asia and the United States, but as a style, there's too much other stuff going on that's progressing way faster than Wing Chun to make it competitive in terms of either a mixed martial arts style practice or in terms of street fight situations against skilled opponents.
I see Wing Chuns anti grappling techniques and I see fast punches that can get through and counter other punches. I also see conditioning in Wing Chun so how come in most videos in yout tube Wing Chunners are always losing. Has there been anyone with Wing Chun that won against someone with other styles such as karate and jujuitsu at an equel level.
It's not as though it's a useless style. There are definitely some good things to learn in Wing Chun, but it hasn't evolved to keep up with sports like western boxing and kickboxing or muay thai or judo or Brazilian Jiu-Jitsu. Those styles see a constant evolution and are constantly seeing new techniques innovated and most Wing Chun guys don't have answers for flying knees, or variations on the thai clinch, or the judo clinch, or for rolling submissions.
I have a few friends who train Wing Chun and they like to work with me and spar in a more MMA style setting, but the reality is that the Wing Chun that they practice simply isn't equipped to deal with even basic wrestling aware of protecting the face. They don't really have an answer for a lot of the techniques that emerge out of western wrestling and the clinch game of judo, and that's a really serious problem, since grappling has taken a prominent role in modern competition.
It's not impossible for Wing Chun to be effective, but the circumstances under which it has to be implemented to be effective are very hard to find in modern competition, which is why there aren't really any successful Wing Chun fighters around MMA, and probably why you're having trouble locating videos of successful Wing Chun fights.