If only the Helltaker were to live that long to enjoy it.
Though frankly the best bet would probably actually Judgement if it weren't for the whole High Prosecutor thing obligating her to end you. She's the easiest to win over in a serious manner and the kindest of the lot.
But if we're talking about an actual long lasting relationship, just shove yourself into the abyss with Beel.
She's my favorite of the bunch and probably the only one you could have a lasting relationship with.
I mean you have several avenues. I'd say Justice is also the most stable, and Lucifer does have the "sitcom couple" vibe to her. And if anythings, a good sitcom will never die, even if it stops being good.
If you think about it, when Helltaker dies, wouldn't he just go to hell and continue living with his harem?
Well given most of his harem wants a mortal to escape hell, he may either have earned their undying loyalty and they go back to hell with him, or they don't.
Lucifer does have the "sitcom couple" vibe to her. And if anythings, a good sitcom will never die, even if it stops being good.
Those knives to the back and shoulder are going to kill him at some point though. Really should have given her a butter knife or some fruit cutter instead for the bananas.