I 
this thoughtful gift idea! Shadow work alongside uncomfortable imagery can be powerful. We need to sit with what unsettles us to understand why it has that effect.
I do agree, Deviant Moon Tarot might work for him. The figures are distorted and there’s something genuinely off about them that gets under your skin.
Another option is the Dark Mirror Oracle - technically not tarot, but the artwork is deeply disturbing in a way that forces you to look at parts of yourself you’d rather avoid.
The Bosch Tarot, based on Hieronymus Bosch’s paintings, has this medieval hellscape quality that feels visceral. Some readers find it too chaotic but that chaos can break through mental barriers.
If he wants something that leaves a lasting impression, look into the Tarot of the Flesh by Victoria Iva. The imagery deals with decay and transformation in ways that most decks won’t touch. Fair warning, though. Once you work with truly dark decks, they tend to change how you read everything else.