What enemies do you find annoying for all campaigns?
Marines: Upgraded Runners, Carriers, Hydra Preds, and Blazer Preds
Predators: Facehuggers(Marines would have some problems with these guys but they can kill them from far away. Whereas Preds have alot of slow close-combat units), Synthetics(DAMN THEM!), Carriers, and Commtechs(I HATE Commtechs)
Aliens: Pretty much a large group of Marines, Spear masters(They do that spinning move many times that knock your Aliens away), Flamethrowers, Hydra Preds, Blazer Preds, Commtechs, and the K-series(Only because your hive and their hive are in competiton for more hosts, and after you knock out certain hosts and lay eggs, a K-series Alien would be able to steal a body or two)