There is also Konstantin, Effie, Queen of the Dragons would probably outmatch him.
Konstantin: I always saw him as a big mouth who could easily defeat lesser vampires, but I don't think he can handle Atlas.
Effie: I agree with you here, to me she's very powerful, maybe even on the level of Lucius, but Effie was pure love

, she would never fight someone from her family and she
didn't deserve to be betrayed in bed 
.
Queen of the Dragons: Perhaps, but we have no confirmation that Norandhil has a wife/partner. But yes, if she exists, she must be incredibly strong and ancient.
Mmm yes, perhaps Atlas is far below the fourth place I gave him

.
Atlas is powerful in his right but he's got a long way to go before he's anywhere near on par with the big names.
It's all because of the harem, he does less and less training

.