For me it's a tiebreaker between Russians, Black Americans, and Mexicans.
There a very cool/chilled out Mexicans out there, but man, some of the most nosey, gossiping, eye-staring, drama queen people I've ever known were Mexicans
As for Russians, I have not had a pleasant experience with them. They always seem ok at first, but then they start acting very condescending, getting dead-serious competitive with you out of no where for no reason, and they're sort of unpredictable. It always felt like they were (metaphorically) trying to non-chalantly stick their leg out and trip you when you're not looking.
Black Americans - There are a lot of cool black people in America, but some of them are just a disaster in human form, very impulsive, quick to get and attitude for small sh!t, and freak out about a line taking too long at a store, but when they're in front of the line, they'll hypocritically take their sweet @ss time. Not to mention they talk about race all the time, when most don't.