Level 91

Total Experience Required 5,103,357 [confirmed]

Level 100 progress: 74.77%

This is roughly:
Killing 17,012 people in Warzone, or...
Killing 17,359 people in Execution, or...
Killing 14,417 people in Wingman, or...
Scoring 3,645,255 points in Guardian, or...
Scoring 11,094,255 points in Annex, or...
Scoring 6,714,944 points in Submission.

Horde (TU4)

Completing 25,517 waves on Casual, or...
Completing 17,012 waves on Normal, or...
Completing 12,759 waves on Hardcore, or...
Completing 10,207 waves on Insane.

Or a combination of the above. Have fun!