Level 78

Total Experience Required 3,025,167 [confirmed]

Level 100 progress: 44.32%

This is roughly:
Killing 10,084 people in Warzone, or...
Killing 10,290 people in Execution, or...
Killing 8,546 people in Wingman, or...
Scoring 2,160,834 points in Guardian, or...
Scoring 6,576,450 points in Annex, or...
Scoring 3,980,483 points in Submission.

Horde (TU4)

Completing 15,126 waves on Casual, or...
Completing 10,084 waves on Normal, or...
Completing 7,563 waves on Hardcore, or...
Completing 6,051 waves on Insane.

Or a combination of the above. Have fun!