Tie between FF4 ad Tactics.

Wiegraff for example I've had two friends restart the game because
of that battle, and many many other annnoying boss (even random battles
from over-training!)

Then, the mother of all f Green Hell's hell...Final Fantasy 4 Hardtype.
God there is no slack in that game. Random battles every four steps and you
have to over-train so much just for one boss and then the next would be even more
harder for more over-training. There is only two ways to buy Ethers and Elixers.
There is only one shop in the world to sell them and they are very expensive.
Elixers are a pain in the butt to buy for 120Thousand each, and then comes
Bahamut and Odin which are stronger than the last boss, and way way too fast
and powerful. Once you've beaten them you are able to summon them,
but you wasted that time proving you can beat something stronger than a
big red mass than can end the Universe countless times with a couple lightning
bolts. Then you feel wasteful after you realize you wasted time.

Waste, waste, waste, waste, waste, waste, waste, waste, waste, waste, waste, waste, waste,
waste, waste, waste, waste, waste, waste, spam, waste, waste, waste, waste, waste, waste,
waste, waste, spam, waste, waste, waste, waste, waste, spam, waste, waste, waste, waste,.