It's pretty hard to top American ones.
1.) Physically and mentally unhealthy. Tend to look like serial killers or retards.
2.) Lack shame. Most can't or refuse to suppress power levels.
3.) Unable to create fanworks (Illustration, doujinshi, fan games, music..) like the Japanese do, that won't rage you until you burst a nerve. For most of the time they're just too shitty.
4.) Extremely blatant inferiority complex towards anything that is Japanese, or Asian.
5.) Probably are at least partially a furfag or an emofag.