The Lawnmower Man is both the winner, and kind of cheating as an answer.
The studio had an existing script called Cyber God that they had been sitting on for a while. When they finally got around to making the movie, they figured if they could stick Stephen King’s name on it, then they might get more people to come see it. So they went out and bought the rights to a random King story called The Lawnmower Man and then changed the title character’s job in their movie from janitor to gardener so he could use a lawnmower at least once.
King actually sued them in order to get his name removed from the movie and won. Then they put it back on for the VHS release anyway.
So it kind of hads to be the worst adaptation because it’s not even an adaptation at all. But also cheating a bit because not really an adaptation.
I couldn’t beat Nelo Angelo’s final fight in the original Devil May Cry on max difficulty. He does massive damage and takes only tiny chips off from your attacks. You have to make split-second dodge/block decisions and then make an instant counter attack and any mistake will cost you 2/3 of your health. I spent days trying to get past him and got him below half numerous times, but never really got close to a win.
One strategy I tried was Holy Waters. They AOE the whole room and cause him to flinch. I was hoping I could use that to create an opening, but the HW animation was too slow and he recovered as fast as I did. Then I thought “go to the shop and max out on them and just crack them all at the start to give myself a leg up”. It helped but not much. But then I noticed, because there was a holy water between the store and the fight, I was able to pick up, that the limit only applied to purchased Holy Waters. You could still pick them up from the world. Also, inventory carries over between plays/level select on the same file.
So, I level-selected and cranked it down to Very Easy and speed ran a middle section of the game over and over where I could pick up like 5 or 6 Holy Waters. Once I had like 50+ I loaded back to the fight and just burned him down entirely with Holy Water.