Level 77

Total Experience Required 2,891,154 [confirmed]

Level 100 progress: 42.36%

This is roughly:
Killing 9,638 people in Warzone, or...
Killing 9,834 people in Execution, or...
Killing 8,168 people in Wingman, or...
Scoring 2,065,111 points in Guardian, or...
Scoring 6,285,118 points in Annex, or...
Scoring 3,804,150 points in Submission.

Horde (TU4)

Completing 14,456 waves on Casual, or...
Completing 9,638 waves on Normal, or...
Completing 7,228 waves on Hardcore, or...
Completing 5,783 waves on Insane.

Or a combination of the above. Have fun!