What Grindelwald likes to come back to after a long day of working at MACUSA and interrogating Credence is a broken and sensitive Graves, too wrecked to do anything but whimper and cry as Grindelwald fucks him.

To make the experience even better, Grindelwald keeps him blindfolded and collared up wherever he's kept. And, he likes to deny Graves of an orgasm each time.

TL;DR Graves is Grindelwald's tortured sex slave