I recently played through the Minecraft modpack FTB's Sky Factory 3 with three of my friends. Technically you don't really finish it per se, but we got to a point where we couldn't do much else without excessive levels of grinding and collectively decided we were happy to call it quits.

It was a lot of fun. I've never been a fan of playing other modpacks because they often focus on Minecraft's weakest points (combat is a big one). SF3 on the other hand focuses on what are, IMO, two of Minecraft's biggest strengths, creativity and the grind. Saying we were somewhat addicted would be an understatement, as I alone managed to put 144 hours (6 days!) in the game in around 2 weeks. And that was just me, my poor computer got left on almost every other night so friends could play on the server while I slept.

It was quite different from vanilla Minecraft which helped everyone avoid the burnout that vanilla+ packs usually cause for us. 8/10, probably wouldn't play it again, but the whole group had a solid two weeks of a fun new experience at the nice price of $0.