Level 91

Total Experience Required 5,103,357

Level 100 progress: 74.77%

This is roughly the same as:

Killing 8,506 people in Warzone, or...
Killing 8,680 people in Execution, or...
Killing 7,209 people in Wingman, or...
Scoring 1,822,628 points in Guardian, or...
Scoring 5,547,128 points in Annex, or...
Scoring 3,357,472 points in Submission.

Horde (TU4)

Completing 12,759 waves on Casual, or...
Completing 8,506 waves on Normal, or...
Completing 6,380 waves on Hardcore, or...
Completing 5,104 waves on Insane.

Or a combination of the above. Have fun!