Level 65

Total Experience Required 1,576,813 [confirmed]

Level 100 progress: 23.1%

This is roughly:
Killing 5,257 people in Warzone, or...
Killing 5,364 people in Execution, or...
Killing 4,455 people in Wingman, or...
Scoring 1,126,295 points in Guardian, or...
Scoring 3,427,855 points in Annex, or...
Scoring 2,074,754 points in Submission.

Horde (TU4)

Completing 7,885 waves on Casual, or...
Completing 5,257 waves on Normal, or...
Completing 3,943 waves on Hardcore, or...
Completing 3,154 waves on Insane.

Or a combination of the above. Have fun!