Level 89

Total Experience Required 4,746,383

Level 100 progress: 69.54%

This is roughly the same as:

Killing 7,911 people in Warzone, or...
Killing 8,073 people in Execution, or...
Killing 6,704 people in Wingman, or...
Scoring 1,695,137 points in Guardian, or...
Scoring 5,159,112 points in Annex, or...
Scoring 3,122,621 points in Submission.

Horde (TU4)

Completing 11,866 waves on Casual, or...
Completing 7,911 waves on Normal, or...
Completing 5,933 waves on Hardcore, or...
Completing 4,747 waves on Insane.

Or a combination of the above. Have fun!