Level 81

Total Experience Required 3,451,813 [confirmed]

Level 100 progress: 50.57%

This is roughly:
Killing 11,507 people in Warzone, or...
Killing 11,741 people in Execution, or...
Killing 9,751 people in Wingman, or...
Scoring 2,465,581 points in Guardian, or...
Scoring 7,503,942 points in Annex, or...
Scoring 4,541,860 points in Submission.

Horde (TU4)

Completing 17,260 waves on Casual, or...
Completing 11,507 waves on Normal, or...
Completing 8,630 waves on Hardcore, or...
Completing 6,904 waves on Insane.

Or a combination of the above. Have fun!