well a book that they printed about the invincble universe states that although the viltrumite race is powerful they weakness is that they reach the peak of genetic evolution,they cannot become any stronger, like mark's dad said to alan there are fewer of them now. The universe is big and like most greedy empires they try to expand their territory to much and they are going to come across beings that will not bow to them and are on the same if not greater strength level such as the battle beast. That is why Alan,Mark, and especially his younger brother have an advantage. Alan as we know has grown strong enough to take on a viltrumite one on one now.Mark's younger brother has an advantage because the race that he comes from mature fast so he will get stronger faster and he has good killer instinct which just needs honing. As for mark i'm not surprised he hasn't gotten better he spends too much time in his social life.Come on youre told by your dad you come from a warrior race that will later come and enslave every human being if they do not comply they will be erradicted. Do you really think i would be trying to create some kind of social life or falling in love, fuck that i'd be training my ass off to be ready to face them.Mark is Part human and part vultrimite when the fuck is his killer instinct going to kick in .