at launch there were bugs everywhere that were game breaking
machine pistols were OP as hell
noob tubes were so overpowered and that + scavenger pro with danger close was just stupid.
terrible weapon balancing
kill streaks were overpowered as **** since kills from kill streaks added onto your kill streak leading to easy high level kill streaks and you don't need to put in a lot of effort for them (I'm looking at you predator missile, harrier, and AC130)
stopping power was way to good
Intervention was straight up a broken gun since it had almost no empty reload
Perk balancing was awful
Akimbo Shotguns
Shotguns being secondarys
Useless equipment (blast shield sticks out)

Thats just some of the issues,