Warhammer: Vermintide 2

You will likely need 1 other person to help you with this.

So the achievement description isn't very clear on what to do here. To get a "Strike" you must use one of the cogs midway into the Trail of Treachery level and hit ~10 rats with one throw. You can shove rats with LT and throw the cog with RT. This can be done on any difficulty, but you will want to pick Champion if you don't have a full team of 4. This is so that you can kill the bots when you get to the cog section. Bring an Ironbreaker Dwarf so that he can tank all of the damage while drawing the attention of the enemies.

Progress about 5-10 minutes through the mission and get to the cog section. Before flipping the lever to start the event down the bots, revive them, then down them again. Now, the bots won't be alive to kill any of the rats (this is important because eventually, the rats just stop spawning if you kill too many, so you want to only kill necessary things like Specials). Find a cog (two randomly spawn), and bring it to the stairs where you flipped the lever. Have the Dwarf funnel the enemies onto the stairs while you're at the top, and when it looks good, throw the cog down the stairs and hope it hits 10 rats. BE CAREFUL not to throw the cog into the machine behind you, as you can't get it back out (but you can also just get the other cog if you do this). The cog is finnicky and doesn't like to go perfectly straight, so you'll have to get used to how the cog moves when you throw it. Even with this strategy, it took 3 or 4 times of getting to the cogs to get this for each person.

I tried the original guide's method of obtaining the Strike achievement both solo (on Champion) and with a partner many, Many, MANY times and had serious trouble completing this. I tried "the stairs" method, I tried "the sawmill" method, and I tried "the alley made by the logs" method, all not working in solo nor in duo.

What did work is we (when I finally succeeded, I had a partner) used the building to the right of where you enter the sawmill area. It's the building with an ammo box, a bomb or healing potion behind a door, etc. What we did was start with two "shielded" characters (spear and shield on Kirellian Handmaiden, Sword and Shield on Kreuber Foot Knight -- I personally liked Kirellian because she could dash past rats and have a two second invisibility to better get cogs and move into position unmolested, and I'm normally a Bardin man). We did this for the extra block and push ability the shields allow. From there, we made our way to the sawmill, and followed the steps above -- downing our bot partners -- then upon starting the event, we dashed to the closest cog, grabbed it, and went into the building as described above.

NOTE: a speed portion (or conc potion for Handmaiden) makes getting the gear and getting into position much easier during this phase. You can always find two speed potions in the cave behind you after the first big dropdown of the level (at least on Champion they always have two...)

Once in the building, the partner currently going for the achievement heads left into the dead-end corridor of the building and drops the cog in a place where they can grab it quickly. The other partner positions themself to the left (if looking out of the building) of the central entrance. As enemies come pouring in the main entrance, player by the door uses their push ability to push the rats down the hallway toward the achievement earner. The one going for the achievement (currently down the hall with the cog next to them) then pushes the rats into a corner of the hallway, so that they're all bunched up. Remember to always block between pushes.

Keep blocking and pushing like this until you count ten rats in the corner (or twelve to be safe). Once done, have the one going for the achievement do one last push, then grab the cog and quickly roll it into the corner with the bunched-up rats. If you've stacked 10 rats or more this way, the achievement should unlock.