2016 Olymic Bronze Bomber Medalist Ivan Dyschko . One of the dudes that was robbed against that racist Femi Olaseni that calls himself Anthony Joshua for some reason.
Valuev is probably the biggest, though he has pituitary gigantism, so he's not exactly a typical specimen. I was tempted to mention the Klits, both of whom were born in Central Asia, though culturally and ethnically they're very much Eastern European. Otherwise you're left with guys like Chagaev and Jirov. Regarding Japanese fighters, most of the really big guys tend (or tended) to go into kickboxing and MMA. Japanese people as a whole aren't actually that small, but there tends to be a massive drop off in skill and athleticism above around 175 which might account for their lack of success at the higher weights.
All the big Asians are in Sumo/Kickboxing or MMA or Math and science professions. At least half of them work for Capcom and other video game companies.