Level 67

Total Experience Required 1,757,767

Level 100 progress: 25.75%

This is roughly the same as:

Killing 2,930 people in Warzone, or...
Killing 2,990 people in Execution, or...
Killing 2,483 people in Wingman, or...
Scoring 627,774 points in Guardian, or...
Scoring 1,910,617 points in Annex, or...
Scoring 1,156,426 points in Submission.

Horde (TU4)

Completing 4,395 waves on Casual, or...
Completing 2,930 waves on Normal, or...
Completing 2,198 waves on Hardcore, or...
Completing 1,758 waves on Insane.

Or a combination of the above. Have fun!