UFC boss Dana White revealed the rudest celebrity he’s ever met – branding the nightmare superstar the “biggest douchebag ever.” White, 56, spilled on Tuesday’s episode of “The Katie Miller Podcast” that disgraced hip-hop icon Sean “Diddy” Combs landed on his bad side after allegedly leaving his young niece shaken when she asked him for a photo at a children’s celebrity charity event. “Oh, Diddy – 100 percent the biggest douchebag ever,” he said when asked who the nastiest celeb he’s ever crossed paths with, adding he wanted to “really f—king stick it to whoever it was.” Dana White revealed the moment that disgraced hip-hop icon Sean “Diddy” Combs landed on his bad side. YouTube/Katie Miller Pod “Tony Hawk used to have these charity events, and when my kids were little, you’d go to these charity events and, like, lots of celebrities would be there.…