Cleared Stage 25.

I've tried leveling up and testing various weapons, and sniper rifles are good. The reason is #1. The mini-magazine tech is great. The mini-magazine tech makes your ammo count 1 bullet, and it's a technique where you reload and shoot, reload and shoot, which increases bullet damage. Since this mini-magazine tech is so good, it's not a great fit for weapons with high ammo capacity like assault rifles. So, to summarize, because the mini-magazine tech is good, it's a perfect match for sniper rifles that have high damage per shot. To clear Stage 25, I think you'll need to upgrade your sniper rifle to purple tier 3 and level it up. And an extra tip! Sometimes it's easier to fight in open fields during gameplay, but when enemies swarm you, it's also quite useful to utilize surrounding obstacles to filter and slow down the zombie rush, as shown in the screenshot. lol