Kingdom Hearts.
Those games may have harder difficulties, but it feels as if they were meant to be played on the easier settings. It provides just enough fight that I can enjoy the combat without getting pissed off that fucking Dragon Maleficent just fire spammed me to death for the fifth time, or that Xemnas once again killed me with his bullshit teleport-grab in the final battle.
The Heartless not only do more damage, but I'm fairly sure they have more health. I remember having to really wail on them outside of Easy, and the Hades Cup being a true buttfucking nearly every time I entered. Not even because of the enemy damage, but because of their HEALTH BEING SO HIGH THAT THE TIMER WOULD HIT ZERO BEFORE I COULD BEAT THEM TO DEATH!
KH is just more fun when you can keep moving forward in the actual story and not even have to think of the difficulty.
Birth By Sleep turned into an extreme rage session for me. I can honestly see no possible way that I could ever beat Xehanort after he has taken Terra's body as Terra. He kills me so hard and uses the most bullshit, insanely cheap attacks and deals such ludicrous damage on Proud that eventually I erased the file, went back into Easy, breezed through Terra's story within five hours from what had taken me nearly ten on Proud, and then repeatedly destroyed Xehanort over, and over, and over, turning it off and reloading the save before the fight at least four times. Same with Ventus fighting Vanitas. What a load of crap.
Mass Effect on anything higher than Veteran. The first for the reason mentioned before with the somewhat clunky combat, but Mass Effect 2...oh my lord. You remember those shutters during the Archangel recruiting mission that you need to close? I was stuck for fifteen minutes on a single side shutter by ONE. FUCKING. PYRO-VORCHA who was camping around a corner. Tried going in myself, killed me. Tried sending in Mordin with his Biotics, downed instantly by the fire as he hopped the wall. Tried simply running past, killed me before I got over the second obstacle.
Eventually I hopped the wall, shotgunned him right in the face, hit him with Mordin's power, and beat him to death with my melee as he reeled. I then proceeded to waste all of my Heavy Pistol ammo by emptying clip after clip into his ugly rat-face on the floor.