I hated Malenia. As an old Soulsborne-veteran that grew up with the impression that equipment and specs don't matter bc every boss is beatable with whatever and just your skill matters, this was the first one that forced me to respecc and use different armor.
Still, with heavy abuse of her AI, completely memorizing her attacks and countless jumping attacks, I was able to beat her with an ultra-greatsword, the arguably worst weapon you can have against her. I would make a video of my tactics against her for you, but ER, for some reason, STILL has no mechanic in place for challenging a boss anew without going through the whole game again, and I'm not going to do that.