Level 98

Total Experience Required 6,429,618

Level 100 progress: 94.2%

This is roughly the same as:

Killing 10,717 people in Warzone, or...
Killing 10,935 people in Execution, or...
Killing 9,082 people in Wingman, or...
Scoring 2,296,293 points in Guardian, or...
Scoring 6,988,716 points in Annex, or...
Scoring 4,230,012 points in Submission.

Horde (TU4)

Completing 16,075 waves on Casual, or...
Completing 10,717 waves on Normal, or...
Completing 8,038 waves on Hardcore, or...
Completing 6,430 waves on Insane.

Or a combination of the above. Have fun!