As much as I love the game, it was stupidly easy. I heard people saying that the final mission was so difficult (Ending C) but it was a walk in the park, and pretty short.
My hardest mission was getting the Police Van with Stingers in. Must've redone that about five-six times.
I did that on first go! Just walked up to it, jumped in, lost the cops! Looking back at the game, the only one that I really found hard was "Burying The Hatchet" the
was a bitch. That's the only thing that springs to mind...
I just wen to the police station, knocked a calling cop out and took it without a problem, I didn't even get a wanted level. And if you think GTAIV was difficult you're not really that good of a gamer I think, cause that game was allready way too easy. GTAV was just a joke, it's more an interactive movie then a game. They trying to get as much money as possible by trying to get in as much casuals as possible. The passive mode and "badrep pool" in online is really one of the most ridiculous things ever to be implemented into a game Imo, it would've been ok in other games, sure, but this is GTA, not some simulator.
edit: the final missions I didn't even have a single problem, so that just nor normal for a game like this.