You began your career on a high note, by personally ending the riots of contaminated thugs in the Outbreak Zone.
How to Earn This Badge Edit
Contaminated in Recluse's Victory Edit
With the release of Issue 7, a single Contaminated enemy appears near the train station in Recluse's Victory once approximately every 45 minutes. However, Positron had indicated on the official forums that the badge will not be accessible to villains at all, even if they defeat 100 Contaminated.
Contaminated in The Ouroboros Initiation Edit
The second mission of the Ouroboros Initiation story arc given by The Pilgrim, available with the release of Issue 11, involves traveling back to Outbreak. Contaminated spawn in sufficient numbers to allow the Isolator badge to be earned.