Level 74

Total Experience Required 2,512,081 [confirmed]

Level 100 progress: 36.8%

This is roughly:
Killing 8,374 people in Warzone, or...
Killing 8,545 people in Execution, or...
Killing 7,097 people in Wingman, or...
Scoring 1,794,344 points in Guardian, or...
Scoring 5,461,046 points in Annex, or...
Scoring 3,305,370 points in Submission.

Horde (TU4)

Completing 12,561 waves on Casual, or...
Completing 8,374 waves on Normal, or...
Completing 6,281 waves on Hardcore, or...
Completing 5,025 waves on Insane.

Or a combination of the above. Have fun!