From the good folks at Cinemablend
In regards to the upcoming Hellboy film being rated R Director Mike Mignola had this to say on the subject
It'll lean in the horror direction, more so than the fantasy direction del Toro was doing. When Neil came on, we decided to go for an R rating, so he doesn't have his hands tied, and so he can go as dark and as tough as he wants to go. I was a fan of his, and when he came onboard, I thought it was terrific: now it's really going to be an action-horror film. It's not that we want to wallow in blood, but when you do a PG-13 rating, you bang your head into rules about how intense certain things can be. I think it helps that Deadpool and Logan were R-rated, and what I've been telling people is that the tone of it will be much more the Logan approach: lean, dark, tough, and not something that stops to show limbs flying through the air.