Anita needs our book help! Oh I LOVE reclusive broken Heroes and the heroines that soothe their souls!!
There’s one that I can think of (though I don’t remember if he was an enforcer) and that was Madeline Sheehan’s character “Dirty” in her Undeniable series (and we see his story with Ellie – though I don’t remember her being so much “sweet” as more like… a strong heroine). Still, this is my guess, or at least a guess with a very similar trope which is Unattainable. I LOVE this trope, and in fact, here’s my 4.5 star review of that one. 🙂
IN THE MOOD FOR A SLOW BURN, AGE GAP, SINGLE FATHER, BIKER BOOK? *oooomph* 
<— BEAUTY AND THE BEAST RE-TELLING IN A BIKER WORLD!!! And I’ve been getting so many enthusiastic comments and anticipation for book #2, that I HAD to look into this (plus, Claire C. Riley is a favorite amongst many of us here). 😀
This is a spinoff of her other much-loved biker series called