Hi
This is a surprisingly tricky thing to do.
One thing that works reasonably well is to do this kind of check:
let D be the distance to the destination
let A be a list of all agents (including this one) inside a circle of radius D around the destination
let Area be the sum [a.radius*a.radius*pi foreach a in A], i.e the total area that the agents in A cover assuming they are circles
stop if Area > D*D*pi * 0.6, i.e if the density of agents is more than 60% inside that circle.
I have posted a test script that does this in this thread: Which options of the asset are best for RTS (like Starcraft II). It is not a perfect script, but it is a good start.
Note that in many cases you can use local avoidance (see https://arongranberg.com/astar/docs/local-avoidance.php) however you may still see some pushing depending on the acceleration and movement behaviors of your agents.