Level 55

Total Experience Required 869,952

Level 100 progress: 12.75%

This is roughly the same as:

Killing 1,450 people in Warzone, or...
Killing 1,480 people in Execution, or...
Killing 1,229 people in Wingman, or...
Scoring 310,698 points in Guardian, or...
Scoring 945,600 points in Annex, or...
Scoring 572,337 points in Submission.

Horde (TU4)

Completing 2,175 waves on Casual, or...
Completing 1,450 waves on Normal, or...
Completing 1,088 waves on Hardcore, or...
Completing 870 waves on Insane.

Or a combination of the above. Have fun!