So far your best beats are lux, monolorhino, grypo, Mammolania, Testacornibus smilonemys. That’s really about it. I mean it is the second best 1v1 in the game. The Problem for many is that for one it has 2 forms of speed control (GA and RS) along with it 4,500 bulk, 30% and 1,500 attack its a real force to be reckoned with. Now in all these counter you notice there is a pattern.
Many have either high hp or high armor or both along with shields. And since magnus doesnt have any armor piercing moves so it stopped instantly by any one or a combination of these defenses. On nemys and rhino they actually have 3 way to reduce magnus’ damage. Distraction, shields, and armor allow these two to always keep magnus under raps. Mammo and testa don’t really do that but instead use there armor, damage output and regeneration to make sure they can tak the hit and out survive it. Grypo uses both its attack buff, regen, shields, counter and no escape making sure magnus will get hurt
They are either immune or resistant to stun: the biggest thing that cause many not to be able to counter magnus is that acute stun. It allows it to set up or deny the opponents a turn to either set up or just hurt it. With it it really only can just speed up slow or just do a rampage.
lots of health and or regenative abilities; many are just able to take the hit and if there close to losing just regen, thats mostly how lux wins.
Now there are other but they require mind game and rng to properly counter. Some like Gemini, maxima, tryko and magna, even dioraj takes some rng as it can take lots of damage or be set up on if it keep get stunned but it can still give magnus a hard time. But thats just from what i can see others like @ElEduardo or @Piere87 are probably better at giving battle sims and 1v1s outcomes than me