Level 90

Total Experience Required 4,923,103

Level 100 progress: 72.12%

This is roughly the same as:

Killing 8,206 people in Warzone, or...
Killing 8,373 people in Execution, or...
Killing 6,954 people in Wingman, or...
Scoring 1,758,252 points in Guardian, or...
Scoring 5,351,199 points in Annex, or...
Scoring 3,238,884 points in Submission.

Horde (TU4)

Completing 12,308 waves on Casual, or...
Completing 8,206 waves on Normal, or...
Completing 6,154 waves on Hardcore, or...
Completing 4,924 waves on Insane.

Or a combination of the above. Have fun!