Aimlabs

“Gridshot” is the shortest task i’ve found so far, at only 30 seconds as opposed to most other tasks being 60 seconds.

This should be at the front of the featured page, and has to be played 100 times for another achievement anyway. So this should be the task you grind out for all the “Complete X Task” achievements.

Doing this 30 seconds task 500 times should come out to around 4.5 hours if you restart at a constant rate. It took me about 6 hours since I just did it while watching movies or youtube videos with controller in hand, and got distracted sometimes. All that’s needed is a press followed by a to restart the task every 30 seconds. So, this could theoretically be done with turbo if you have a controller constantly spamming those two buttons! Making this something you could leave overnight.

As Darkwing mentioned in the comments, “if you go to Game Settings and set the Countdown Timer to 0 it will save you 3 seconds each task. Adds up”
An easy way to save 25 minutes!

Just do this 500 times and the achievement is yours! Make this the last achievement you go for, so that you don’t have to AFK as much.