Level 27

Total Experience Required 100,218 [confirmed]

Level 100 progress: 1.47%

This is roughly:
Killing 335 people in Warzone, or...
Killing 341 people in Execution, or...
Killing 284 people in Wingman, or...
Scoring 71,585 points in Guardian, or...
Scoring 217,866 points in Annex, or...
Scoring 131,866 points in Submission.

Horde (TU4)

Completing 502 waves on Casual, or...
Completing 335 waves on Normal, or...
Completing 251 waves on Hardcore, or...
Completing 201 waves on Insane.

Or a combination of the above. Have fun!