Here's Level-5's Rogue Galaxy on the PS2 for example. 10-stage final boss. The first two stages are easy, because you can use your normal party, complete with mutual healing and revives. Then they split up: each of the eight main characters, including the ones you never used, has to fight a real boss's body part.
Two of the fights are identical and have you fight a sub-boss, that (if you get the pattern) will never hit you over the course of those several minutes it takes to wear down the long health bar. Two other fights are identical too and are slightly more dangerous, in the sense that the sub-bosses can actually move. Then there's a stupidly easy one, where your character will most likely be able to "shoot the core" to death before its guardian can even scratch you. The next boss can be stunlocked to a quick death. The penultimate boss hits for about 9 damage if you block, while the character facing it most likely has at least 800 HP.
Then the really-really final boss comes, and it turns out that not only does it have attacks hitting a third of your health bar, but it can chain a few of them so quickly, you won't have a chance to heal. Naturally it also has an exploitable pattern, however you won't know it the first time you get there.
Now here's the best part: no continues between the stages. No try again. No revives, since everyone is solo and no one else is there to throw a potion. Almost every boss in the final 8-chain can hit for 1/4 or 1/3 of total HP if you don't know the patterns, and if you do, is wastes your time by having way too much health. Aargh!