I wouldn’t worry. If their skills are bad enough that they have to resort to getting their mons illegitimately, it seems unlikely that they would be skilled enough to know how to actually use them properly. Besides, I don’t think it’s actually possible to bring hacked monsters into pvp anyway.
It’s perfectly possible for someone low ranked to gain a legend and train it to its second form. What isn’t perfectly possible is swiping a monster that hasn’t actually been released yet, so yeah, FameSmilezz is definitely guilty. Troyboy and dragonlord seem legit though.