The Incredible Adventures of Van Helsing III

*Note that this was a working solution before the first patch and I have no idea if this still works.*

Very easy chevo to get and you just need only one friend instead 20 different people. Just follow these steps:

1. One of you creates a multiplayer game, story mode is preferable. NOTE that hardcore characters do not count so just simply create a new character. Both of your characters must be at the same point in the game also.

2. Player who created the multiplayer game invites the other one. During the loading screne there should be 5% progress in both your achievement counters or just one of yours. NOTE that there could be times when neither of you will not get any progress at all so do not panic.

3. Once you the loading screne is gone and the game informs that your partner has connected to your game, simply one who created the game will quit the game from the dashboard and load it again.

4. If you notice that both or neither one of you is not making any progress in the achievement counter, then try to switch roles between each other.

5. Rinse and repeat and you should have this achievement in under an hour if you are lucky.

Happy hunting

If you have two XBoxes and an alternate Gamertag to use, I found this to be a much more efficient way to unlock than the other solutions here (which may work better for you in some scenarios, like when both Gamertags are trying to unlock the achievement). Please be aware that this method will only make progress on one of the GTs, the one that is not hosting the game.

1) Make sure your Gamertags are on each other's friends list.
2) Start game on both consoles - I had my alt tag running on my Home XBox (an XBox One X) and my main tag running on a Series X. This let me take advantage of the Series X's shorter loading times.
3) Turn on the achievement tracker for your main tag so you can see it progressing.
4) Create a new character on both consoles so that both tags are at the same point in the story.
5) On the alt tag, go to Multiplayer option, start a new game, and wait for it to load you into the first map.
6) On the main tag, go to Multiplayer option, select Join Game, then select your alt tag from the list of Friends.
7) Once the main tag has joined the game and you see the tracker progress by 5%, hit Start on the main tag's console and choose Exit from the main menu. You do not need to fully quit the game, and you do not need to do anything on the alt tag's console.
8) Repeat steps 6 and 7 until it unlocks.

Credit to Poat540 whose comment in another solution gave me the idea, all I did was write it up for use with an alt tag.

I was able to get this achievement with only one other person, even after the supposed patch.

One person sets up the game and invites the other. Once the other player joins, both press the home button and quit out. The person who joined should leave first.
This should count for both people.

We were having a problem where it wouldn't count at all for a bit. Resetting the Xbox seemed to fix it.

Not unlocked yet but it seems that you dont have to play with 20 different people. I played with a friend and after a few dis- and reconnects the achievement progress is about 10%.