every Cerberus wave is fun if you have a headshot capable weapon.....unless you're the host. Then when you reach w8, you better save 9 missiles and several TCP's worth of grenades for the bullshit that is about to ensue, unless you brought a stagger weapon, which makes the entire faction a huge joke no matter the difficulty .
The thing with Cerberus is that with the wrong kit they're a pain in the a*se ... with the right kit (AV especially) they're laughably easy. In PuGs though I see more "Mission Failed" against Cerberus than any other faction. However, no matter the kit, every single unit has something about it that annoys me.
Trooper grenade spam
Centurians have almost Marauder levels of damage output AND smoke grenades (I hate the way smoke grenades remove melee lock)
Nemeses instantly shield strip all but the most tanky units, have that ridiculous hop and are always lurking somewhere stupid at the end of the wave
Engineers - I hate wave 7 gold because of the turret spam
Dragoons are idiotically suicidal but they're so often with Phantoms which can lead to stagger > shank > spectator mode if you're not careful
Atlases are such troll units, a bazillion shields, synch-kill to screw over melee kits, homing rockets with stagger and DoT and bloody smoke grenades again - weirdly they're probably my most hated Cerberus unit
Aaaand Phantoms - the biggest problems are that they can insta-shank you if they've taken a swipe at a team-mate and that they're often with 'goons - 'goon or Atlas rocket stagger and it's shanking time.
There are only 2 things I enjoy about fighting Cerberus:
1: Sabotaging Turrets and having them kill the Engies
2: Mission Complete - it's over and in U/U/G that means you know the next game won't have Cerberus!
The list of things that annoys me about Geth is paltry by comparison.
Prime stagger and turrets they can throw through walls
Bomber CQC zapper (stagger)
Hunter cloak that has the same melee-lock breaking effect as smoke grenades and the stagger from their GPS
Triple-tap rocket troopers
... and that's it.