This can be completed in under an hour.
Set up a Solo Custom match. Set the following conditions:
Mode/Map - Arena, any map
Map Effect - Left it blank personally since there was only weather options.
Extras - Favour monster, no strikes, set the monster to level 3, monster armor 100%, 1 round wins
Go into the match as a monster. I picked Wraith and chose his level 3 Supernova, Level 3 Warp Blast and Level 3 Decoy (but never used it) using the Damage perk. To make this easier, make sure to remove Maggie (to eliminate Daisy) and Lazarus (to eliminate revives). You should be able to beat the hunters in around the minute mark using SN and WB.
Once you've killed the hunters, you get a win. Repeat 24 more times and you get your achievement.
EDIT: Credit to SilentRich69 for the details on the Hunter selections and for supplying a video using this solution