The Battle Bricks: 3 star Terminator (gachaless and 3 slot only)

Honestly, if your battlers are level 25, it was a piece of cake. Level 20 units could work but takes much longer. Rail is not a good option due to the amount of peons it has. All battlers are level 25 and base is level 16.

How I beat it:
Upgrade bank while waiting for the peons to arrive. Once they reach halfway, spam trowel and battler occasionally(start spamming right away after bank is level 6) while upgrading bank to not only bait the peons but also the terminator's attack. Get at sniper once bank is level 7. After that, keep spamming everything while and after upgrading the bank to max. Use gatling cannon at all times once it's ready as it can help prevent the sniper stack being killed from terminator's special attack. Repeat the process until terminator dies. After terminator dies, spam only trowel for safer meatsheilding due to the walls(spamming only battler works as well however has lower health than the walls. Don't spam both trowel and battler as they can clog up the unit limit quickly) and snipers for pushing to the base. Use gatling cannon to speed up the pushing process.