Level 97

Total Experience Required 6,234,451 [confirmed]

Level 100 progress: 91.34%

This is roughly:
Killing 20,782 people in Warzone, or...
Killing 21,206 people in Execution, or...
Killing 17,612 people in Wingman, or...
Scoring 4,453,180 points in Guardian, or...
Scoring 13,553,155 points in Annex, or...
Scoring 8,203,225 points in Submission.

Horde (TU4)

Completing 31,173 waves on Casual, or...
Completing 20,782 waves on Normal, or...
Completing 15,587 waves on Hardcore, or...
Completing 12,469 waves on Insane.

Or a combination of the above. Have fun!