Tricks within the game are accepted, Kakero. But console commands and TES godly items are cheating. And anybody can win cheating. I guess you could even kill dagoth ur with a good enough item... he regenerates hp and is invulnerable, but if you deal, say, 1000 damage in a hit, he should die.

nobody will know that you use cheat to win if you didn't tell them in the first place. they'll always think that you defeated vivec with a level 1 character.

Only if they are fools ;) . And obviously there is something about your dignity...

vivec's spell is like lightning poison frost and drain health all in one

Quite a punch. But if you dodge it and he runs out of mana, he's dead meat.