I happen to think that Death from Castlevania: Chronicles in the Original mode is a bit excessive. The original Death was hard enough, but you could get lucky and get a triple-shot Holy Water or Cross and spam him to death. This guy can now throw his scythe wherever you're standing while you try to dance your way out of the rain of tiny blades or just decide, "Gee, I'm getting hit pretty hard. But I don't have to put up with this, so I'm just gonna go invincible for a moment and then trap you in place while spewing homing skulls non-stop." Jerk. Thank heavens for Herbs and an almost endless supply of hearts.
A more current one would be a game I played briefly a while back - Godzilla: Destroy All Monsters Melee. Almost every fight pits you against Mechagodzilla at the end, who has the arena rigged in his favor with dozens of turrets and spacecraft that chip away your health unless you manage to break through the forcefield and hide behind a building. And as for the boss itself? It laughs at edged attacks, instantly heads for power-ups whenever they appear, and on Hard, blocks most of your attacks and retaliates by grabbing you and propelling you up into the air with his laser eyes. Attempting to fire back from a distance? It interrupts your attacks with a quick burst of laser and then lets loose with finger missiles. And if you get hit by its Rage attack, then congrats, you just discovered the most damaging move in the game, the hard way.
This wouldn't be so bad if it weren't for the fact that in order to unlock more characters, you always have to beat the game with whatever monsters you currently have available. And some of them are just screwed right at the starting gate. Gigan has almost exclusively edged attacks, a cruddy beam weapon, and lacks hands, which obviously makes grappling a problem. Orga is slow as %&^! (and looks like it, too), which means that any attempts to grab or punch will be blocked, dodged, or cut off with a quick one-two. Megalon...hey, it's like Gigan, but with an unbelievable weakness to getting hit with blunt objects. You know, like fists. Anguirus, lacking damaging attacks or a decent breath weapon, relys on blocking with his spiked back and then attacking the opponent while they shake their wounded limbs after being so dumb as to punch a pincushion. Of course, Mecha simply shoots a plasma bolt out of his gut and laughs, then unloads with those ^$#&* rocket fingers.
So on Hard mode, the best thing you can do for these characters is try to hunt down power-ups and pelt Mecha wih buildings from a distance. Occasionally, try for a throw and stomp on his limp body afterwards. And that takes some luck - pray for health.