Golden Brewery Iron with Asra and Lvl1 Shadow Archers only (Impossible) - Kingdom Rush ReVengeance

Here's a fun fact: building more lvl1 towers will technically give you more cost-effective DPS than upgrading fewer ones. This obviously doesn't take into account range and abilities, but it's still a fun fact to know. So, I decided to test it out and beat this challenge with lvl1 Shadow Archers only. They performed way better than expected, as the damage from all those cheap towers quickly racked up. I also tried the same stage with only 3 lvl3 Shadow Archers (which cost about the same as 14 lvl1 archers you see here) and they performed slightly better (probably due to larger range and better fire rate allowing few, well-placed towers to farm more damage as most lvl1 archers here are not really engaged in combat simultaneously). Still, if you're gold-starved, it's a neat fact to remember and you shouldn't underestimate the power of cheap DPS.