Resident Evil 4
I've tried a dozen times over the past 15 years and have just never made it to the end.
Edit: Well… seeing as I've clearly offended someone I'll explain why.
When RE4 came out I was about 12 or so and me and my younger sister would play it but we'd always get too scared once we got to the castle

we tried so many times but the chanting monks with the medieval maces scared the shit out of us.
Fast forward a little over a decade my sister spent 3 weeks in the ICU from a still undiagnosed auto immune attack. She almost died, it was pretty awful.
Once she was stable I brought my Xbox One and a monitor into her hospital room and we played RE4 together like when we were kids. We made it up to the boss fight with the army guy who can dodge all of your attacks except the knife

but she was discharged and we still haven't had the chance to sit down and finally finish it. I promised her I wouldn't finish it until we could do it together, but she lives 3 hours away so it's kinda hard to get together long enough to do so.
She's gonna come stay with me and my wife for a bit over the summer so we can try then.