Can someone explain to me how they did that monstrosity?

That’s either a) something fake stuck on, like foam
or b) fucking cursed swelling. It seems to be very neat though. Weird

What @creativedragonbaby said

Herpes tattoos

Looks like an allergic reaction to the red ink. Then again, the black looks faded, so it's at least a few years old. Maybe they redid the red ink?

Keloid Tattoo

It's just an allergic reaction to the ink (probably unsanitary equipment) it causes the skin to bubble and burn, causing blisters like injuries full of puss and whatnot, then you get like burn scars if the skin heals properly

blue waffle strikes again... only this time as a rose.
Jack dodged a bullet.

As anthracite said, this looks like it is a severe reaction to the red ink, and is likely also infected, and possibly turning into a keloid (as Nelson said).
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From what I've heard, tattoo ink doesn't have much in the way of official regulations, and red tattoo ink in particular can contain a variety of metals that skin can react VERY poorly too.
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Here's another example of a "3D tattoo" where you can see only the areas that had red ink are inflamed.
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scielo.br/img/revistas/abd/v92n5//0365-0596-abd-92-05-0748-gf01.jpg

Thanks guys! I did not know that about the red ink (granted I don't know a lot about tattoos), that's interesting.
I'm also slightly concerned about the 38 people who liked this post, there's nothing to like here!

I thought the first pic was someone bending over at first