I am not all defending Cerberus, but I am curious as to who you think is more formidable in comparison.
Well someone who isn´t a complete idiot, getting saved by the "power of the narrative" or plot shields on the invincible level? The Citadel coup as written, was unbelievable bs, even the basic plan made no sense. Their research experiments are risky and moustache twirling evil for the lulz. TIM´s whole plan for the mission against the Collector is a mess because the writers forgot, that the whole plan was based on fourth wall breaking. Every time you encountered Kai Leng, he was total wimp, until he got the power of the cutscene to turn you into a drooling moron, letting the player watch as Shep turned into someone with the intelligence and aim of a random mook from Arrow or a SW stormtrooper. Every higher up in the Cerberus ranks is a total sell out who spills the beans as soon as you imprison them (I give the the dignity of death, even in pure paragon, these deluded fools).
Oh my, the guys you meet are an intel agent who thinks it´s a bright idea to break free in front of three armed people, some corporal styling himself as the cliché of a general, who taunts you with "this time our control over these highly dangerous creatures will hold" (we see how that turned out on Horizon, when the Reapers actually bother to take back their toys), a dude who wears a stupid mask and a grudge because daddy loves Shep more than him. And last but not least, TIM, who tries to impress his doc wth no anesthetics for this invasive surgery close to his head(where flinching would probably lead to a miscut and ehm complications, bleeding out or brain matter on the floor).
Yeah they did some impressive stunts when they showed up but most of the time, it left you in a befuddled state why and how it´s possible that these guys are actually showing up there.
And even if all that changed and their roster wasn´t something out of a cartoon and their plots actually formidable, they were still unable to execute their own agenda but worked for an enemy with a completely contrary agenda. It´s not even like "ups, we fell into a very sinister trap laid by our enemy" but "ah yeah we totally do it, even if it makes no sense, because we are unwitting , indoctrinated pawns and everyone with a brain already left."