People were complaining about snipers being OP, they got nerfed.
People complained about Thunder, now he is almost never played.
Same with Javelin and I can probably find more if I take the time to think.
But Nader has been overpowered since I can remember. 90 damage grenades with only a 5 second cooldown and she has 5 of them.
Nader, Redeye and Aura are arguably the most overpowered mercs in the game. Aura is getting nerfs (they are really tiny but if it keeps going this way she will eventually be balanced), Redeye is still OP but he isn't played often and those who play him are mostly noobs and can't abuse his OP'ness so I won't bother talking about him in this post.
When will Nader finally get the nerf she deserves?
It could be a longer cooldown, less nades, increased fuse time, slower fire rate (for the grenade launcher), less AEO damage, smaller blast radius. I don't care what happens, just anything to reduce the effectiveness of spamming grenades.