Pink Bean

Yes of course. Horned Tail was once thought to be unbeatable. Same goes for Zakum.

Yeah, but Horntail is juts another big rock with a ton of HP. There's very little chance of INSTANT DEATH and any moron can kill it with enough time and firepower. With Pink Bean death is lurking at every corner. Melee need 18k+ HP to survive and 23k+ if they don't want to risk getting 1hko'd by touch. Ranged classes need 8k+ HP to survive, and a simply ridiculous amount of HP to survive the dreaded Genesis attack, which only attacks in front of him, but has a huge range. Most of the battle requires Pink Bean being oriented in the right direction and positioned in a location where he isn't poised to run everyone over. And to top it all off you only get an hour to do it.