What ruins the game for you?

I don't see rocket glitch abusers on that list unless that falls under bugs, I'm not sure.

I'd rather take on a bunch of pugs that know fuckin squat what to do on gold than have those cancer rocket glitchers in my lobby (unless they were my BSNer friends I could care less). Ban them get them out of here, take some shots, take a shower and pretend they never existed in my eyes.

1) Rocket Troopers - hey, why don't shoot that rocket at me
2) Rocket Troopers -  hey, you just hopped in and out of the cover, why not shoot it again
3) Geth Primes - just cast those drones, I don't mind your buggy ass
4) Shockwave spammers, or useless power spammers in general - Yup, your shockwaves on flying Pretorians and stationary banshees are appreciated, keep up the good work. Screenshake is appreciated as well, sometimes my aim is off, but screenshake just adjusts it for perfect headshots
4) Nemesis - get over here you slimy bitch
5) W11 Spawn nukers - get over it bitch, you ain't catching up with me, it is pathetic. L2ScoreWhore scrub!
6) Lamer - it is pathetic power and should only be used with Vorcha when completing challenges
7) Rocket Troopers - Fuck you, I see you rocket glitching over there
8) people using wrong mods on their weapons at this point of the game. I am talking about 100.000+ CP players here. Recently I had really highly ranked players using Venom with both piercing mods and Drill rounds. Wanted to tell him, but then I saw his rank so I didn't - it felt like telling 60 year old that Santa isn't real. 
9) Have I mentioned Rocket Troopers and Geth Primes? Funny how I hate them, but forget to mention them as often as they deserve.

Ah, nothing really ruins the game for me, but my pet peeves are the connection issues, the weird incompatibility between the game set ups when you can't group up with someone, and one particular troublesome habit when the folks try to stake out the extraction zone right away in Wave 11. That one is somewhat of a BioWare's fault, not players', because of the way that assignment is worded being misleading.

I don't mind hitting the deck if I make a stupid mistake.
I don't mind the stupid AI making me look like an idiot (I'm looking at you, Nemesis)

But lag gets right on my tits.

Impressive

EA/Origin should be on the list too,but I guess bad connection would be close enough.Several of my friends just get caught in an infinite loading screen.Bad connection also happens to describes their relationship with the player community as well.

being a peasant, I've never had to deal with it.

So why do you have an Origin ID in your profile?

It's because it trivialises the game too much. Multi-primes and staggers everything, through walls or not, and great bugged double damage on all defences (that comes with the free debuff too if you're one of the smarter pugs). Snap freeze has no limits and easily the most broken power in the game. Game isn't that much fun when all challenge is removed. I don't mind it so much on the N7, as they can melee and incinerate too, but on AIUs with no cooldown penalties and nothing else do do but spam it as quickly as possible, forget it.

This a good question.Inquiring minds would like to know.

Everything on the list ruins the game and I only manage to endure it because of a combination of Turians and masochistic impulses