Level 60

Total Experience Required 1,182,611 [confirmed]

Level 100 progress: 17.33%

This is roughly:
Killing 3,943 people in Warzone, or...
Killing 4,023 people in Execution, or...
Killing 3,341 people in Wingman, or...
Scoring 844,723 points in Guardian, or...
Scoring 2,570,894 points in Annex, or...
Scoring 1,556,068 points in Submission.

Horde (TU4)

Completing 5,914 waves on Casual, or...
Completing 3,943 waves on Normal, or...
Completing 2,957 waves on Hardcore, or...
Completing 2,366 waves on Insane.

Or a combination of the above. Have fun!