There have been some LONG boss fights.
This wasn't the longest, but it was the one that nearly made me quit after nearly an hour and a half: the final boss of Xenosaga Episode II. I kept NEARLY killing it, but when it got near death, it just kept pulling a "I'll heal myself back up to full health" spell and I had to repeat the same cycle over and over and over until the AI basically just decided not to use it... after nearly 2 hours of that monotonous cycle.
Others that lasted forever include the bosses of Bayonetta (those bosses just don't stay DOWN) and plenty of Final Fantasy bosses have those long, multi-stage forms (Edea wins for me... also because I died my first time when she was nearly dead and had to do it all over).
Others I'd throw out include Ninja Gaiden bosses who kill you in one or two hits, yet they absorb dozens upon dozens of attacks like your sword is made of wet spaghetti noodles. And Liquid Snake also wins my "most persistent boss" award for being the villain that you kill over and over and over but he keeps coming back... even if that means his silly severed arm is still causing you problems three games later.
This wasn't the longest, but it was the one that nearly made me quit after nearly an hour and a half: the final boss of Xenosaga Episode II. I kept NEARLY killing it, but when it got near death, it just kept pulling a "I'll heal myself back up to full health" spell and I had to repeat the same cycle over and over and over until the AI basically just decided not to use it... after nearly 2 hours of that monotonous cycle.
Others that lasted forever include the bosses of Bayonetta (those bosses just don't stay DOWN) and plenty of Final Fantasy bosses have those long, multi-stage forms (Edea wins for me... also because I died my first time when she was nearly dead and had to do it all over).
Others I'd throw out include Ninja Gaiden bosses who kill you in one or two hits, yet they absorb dozens upon dozens of attacks like your sword is made of wet spaghetti noodles. And Liquid Snake also wins my "most persistent boss" award for being the villain that you kill over and over and over but he keeps coming back... even if that means his silly severed arm is still causing you problems three games later.