Guts & Blackpowder - 20 Waves Solo, No Kiting 

Credit to ‪@cefibe‬ for the strategy
I built a bunch of barricades at the front so the zombies would be able to get killed by either the first bomber or my grenades. At wave 15+ you will sometimes get overwhelmed and have to jump, but it shouldn't be as difficult as solo vardohus since no extra zombies will spawn.
Attack if there aren't too many zombies, shove if you still have multiple barricades left and there's a lot of zombies, back away and use grenade if there are a massive amount of zombies and you have barricades to hold them back.