Level 85

Total Experience Required 4,073,479

Level 100 progress: 59.68%

This is roughly the same as:

Killing 6,790 people in Warzone, or...
Killing 6,928 people in Execution, or...
Killing 5,754 people in Wingman, or...
Scoring 1,454,814 points in Guardian, or...
Scoring 4,427,695 points in Annex, or...
Scoring 2,679,921 points in Submission.

Horde (TU4)

Completing 10,184 waves on Casual, or...
Completing 6,790 waves on Normal, or...
Completing 5,092 waves on Hardcore, or...
Completing 4,074 waves on Insane.

Or a combination of the above. Have fun!