Markus would win with or without his hybris powers. He is Viktors sire, older, stronger and more powerful as well the first vampire and a holder of the corvinus strain. Even their father who was simply immortal was able to kill hybrid Markus if he felt like it.
Up until the point of the first movie after Markus went to sleep, Viktor was the most powerful. But he's not the most powerful overall as the Corvinus strain purebloods and hybrids are naturally more powerful. Also he was the progenitor of the vampires. He was already 100 years old or so before he even turned Viktor.
If that's the case, then Selene straight up lied. She took Viktor out but needed Alexander's immortal corvinus blood to beat Markus. Are you saying normal Viktor was more powerful than Hybrid Markus, who is the only version Slene knows of?
She took Viktor out with a surprise attack. Swap Viktor out for Marcus under those same circumstances and he dies too. Vitkor defeated Hybrid Michael. Hybrid Marcus stalemated Hybrid Michael. Viktor was unreasonably OP.
You're gonna ignore how Viktor beat Micheal who had been a hybrid for all of 5 minutes? While Markus who was the new hybrid on the block killed Micheal the first time they fought and beat him so bad Selene had to help him out with first immortal blood at the end of the movie.
No relevance is ever given to a hybrid being new or not iirc. Michael stalemated Marcus in the back of the pickup before Marcus bfr's Michael. The second time Marcus sneak attacked him and beat Michael without even giving him a chance to fully transform.