The special thing about Cassius was that he had two separate STR rolls upon processing, leading to absurd 200+ STR rolls. That was removed because it was not intended behavior. The best he has now is Brawler + Crackshot + Malevolent + Warrior. Aaron Krueger can roll all of that and get Berserker. Cassius is still strong, but Aaron should edge him out on melee once properly trained and with the right rolls.
Of course, the strongest melee NPCs that can be acquired normally in the newest patch of the alpha is a titan body type son of the MC with Berserker + Crackshot + Malevolent starting trait and then an Educator to train Brawler + Warrior. Warrior can be trained too via the dojo. This, of course, takes some time to set up and requires Mountain Man and STR 130+ on the MC to even have a chance to roll (1/3 chance). The alpha (and the future public release) increases the STR training cap of a titan body type to 200.
Without Mountain Man, the MC (STR 130+) can only have sons up to Herculean body type (1/3 roll chance). Herculean sons with Berserker + Crackshot + Malevolent still hits really hard though. They're Aaron, except with Crackshot.