Awarded for surviving 10 consecutive waves.
This is pretty easy to do however I recommend the following loadout:
1.Machine Gun
2.Machine Gun
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After wave 10 invest in:
3.Rockets
4.Rockets
Just keep your distance from the enemies who often clump together in the middle of the platform. Circle them and just spam them with MG fire.
I do a full playthrough upto wave 60(You see the final boss at 50 and it then repeats below)