According to:

Traditional physics predict that for every charged particle, there is an oppositely charged one. Therefore, an electron will have a positron, which is positively charged. An anti-proton for a proton, and an anti-quark for a quark.

However, supersymmetry goes beyond in postulating that there are 2 to the power of N numbers of such symmetries, where N = the number of properties such as charge, color, or spin. Therefore, we have things like supergravity and superneutrinos and so on.

What happens when 2 particles, an anti-matter and matter particle, were to collide?

Above: They neutralise each other and convert nearly all of their mass to energy.

Then here is an urban legend:

A doppelganger is an exact replica of a person, and it normally connotes bad luck, because once you see yours, like Abraham Lincoln and John Donne did, then you will die shortly after.

Technically this is correct, because supersymmetric theory predicts that there are 2 to the power of N universes, each with their own properties. So if we have charge, spin, and color, we have 8 different universes, each looking exactly like ours, but with different charges and properties. Within them, you will find a person exactly like you.

What happens when 2 of these people from different universes encounter each other? They explode. Literally if they shake hands.

So what happens when you get 2 monsters and 2 hunters of the same kind like this?

Well, you got it:

You get an explosion like the one behind this man.

Therefore the game should be programmed to crash.