Level 89

Total Experience Required 4,746,383 [confirmed]

Level 100 progress: 69.54%

This is roughly:
Killing 15,822 people in Warzone, or...
Killing 16,145 people in Execution, or...
Killing 13,408 people in Wingman, or...
Scoring 3,390,274 points in Guardian, or...
Scoring 10,318,224 points in Annex, or...
Scoring 6,245,241 points in Submission.

Horde (TU4)

Completing 23,732 waves on Casual, or...
Completing 15,822 waves on Normal, or...
Completing 11,866 waves on Hardcore, or...
Completing 9,493 waves on Insane.

Or a combination of the above. Have fun!