Uh...*glances at Mordin Solus avatar*
Do you really want me to get into that? Because between Kai Leng, the decision to have Cerberus occupy the role of central villain when the Reapers should have taken center stage, the From Ashes DLC, insulting everyone's intelligence by dumbing down the arc-villains' motivation to "different races organics and synthetics are just too different to ever get along" and treating that like wise counsel instead of being almost a direct invocation of the myriad attempts at justifying racism through science, more or less using Dragon Age Origins as the story template for Mass Effect 3 (And if you're doing the 'gathering allies to push back against the invaders' bit in the final act, you've done something wrong), shoehorning in a PTSD story for a new trauma...which can be downright bizarre in light of some of ME1 backstories, to say nothing of the weirdness of how the death of one child haunts Shep in a way that everything else doesn't (excluding the backstories, no trauma over getting spaced, burning up on reentry, hitting terminal velocity and ending up a pancake in the opening of ME2? Why this weird kid rather than Jenkins in ME1? The sacrifice of a friend on Virmire?), the sheer idiocy of "we don't know what this machine is, but we know that it's an anti-reaper weapon that's meant to slot into something that even the designers didn't know about", everything about what is derisively referred to as the 'starchild'...suffice it to say that if I went into detail, I could probably hit the post character count limit before I even started talking about another game.
Though on a much lighter - and probably less discussed - note from the same game...the Victory Fleet cutscene. The intended reaction is obviously 'hell yeah!", but I was practically screaming at my computer "WHAT THE FUCK ARE YOU DOING?" See, I love lore and world building. You give me a reasonably well written codex, and I will read it cover to cover...and I did that for Mass Effect. And there are a few interesting entries about fighting the Reapers, such as situations where their defenses are taxed, what kind of weapons are effective against those defenses, innovations that have been made in response to what they learned in the wake of Sovereign's attack on the Citadel, how much concentrated fire they can take, tactics that have caught them off guard in the past... And then comes the Victory Fleet's arrival wherein they proceed to throw strategy to the wind, park all the ships and engage in line firing while in orbit. It's almost as tailor made to maximize the enemy advantage as Game of Thrones' Battle of Winterfell, and it's so frustrating.