Guide to beating Razor Queen:
1) (This assumes you have already seen a razor queen) Have the reactive armor and box gun equipped.
2) As soon as you start, set up the box gun in a corner. Dodge any of the RQ charges and swing at its head as it passes.
3) After the RQ lunges, the box gun will be ready and fire. This will distract the RQ and it will go straight for the gun, ignoring you. Now, you try and get as many hits in at its head as you can while it is distracted, but make sure you avoid its side blades, the long thin ones.
4) I believe that the reactive armor does 3/7 hits to a razor queen as it explodes, and so if you can hit it three times while it is distracted, you just have to get hit in the RQs vicinity.
Hopefully this helps, this is just what worked for me. On a side note, it may happen that when you kill a RQ in a rematch, you get awarded 2 kills, getting you two awards. If you think this is helpful, up for others to see.
Woah, I was freaked out when i saw an amalgam. There had been a void eater on screen, an inkie hit me, and then it was there. I thought it was another evolution from green gloopies.