[Snake]

Because upgrade was in a good place, he butt-dunked almost every sorts of buffs and debuffs. Also eh, it's not like if there's zero counterplay towards ye' olde' engineer class.
Just have:
1- A gun, preference being some Borneblood Jackhammer.
2- Interference Shell, Null Shell.
3- Proceed to make them cry as you remove their ability to heal, and the Upgrade buff if you time your Cooldown with a good positioning.
(I'm pretty damn sure Romek can do this and walk away with sunglasses and back turned to the explosion.)
If you're playing something like a Soldier, or Duelist. HEE-HEE, welcome to YOUR counterplay. Engineers are simply the Rock over Scissors, in this case.

And I mean, really, I'd rather complain about Hexer and Menov's Fang doing 'unresistable' 80% of your MAX HP as damage, out of only Poison while the caster just waddles away. Wdf is the counterplay?

Or if you manage to silence them while poisoned, they just fart a Menov, cuz this is a god damn SKILL and can't be muted. And you have to be a specific >RACE< to win against those, no class, no anti-toxin, not even the new alchemist snake-eater potion thing (forgot name), generally nothing. Just a fully leveled new char that will take another year to make, no simple class swap. So I can say they do have 0.1% chances to be counterplayed.