Level 63

Total Experience Required 1,409,509 [confirmed]

Level 100 progress: 20.65%

This is roughly:
Killing 4,699 people in Warzone, or...
Killing 4,795 people in Execution, or...
Killing 3,982 people in Wingman, or...
Scoring 1,006,793 points in Guardian, or...
Scoring 3,064,150 points in Annex, or...
Scoring 1,854,618 points in Submission.

Horde (TU4)

Completing 7,048 waves on Casual, or...
Completing 4,699 waves on Normal, or...
Completing 3,524 waves on Hardcore, or...
Completing 2,820 waves on Insane.

Or a combination of the above. Have fun!