Are you looking for a good padlock or lock cylinder?
If you are looking for a lock that is difficult to pick, you should look for locks that are difficult for amateur lock pickers to pick ๐. When lockpicking, different colored belts can be achieved, ranging from white (easiest) to black (hardest). Each belt has certain requirements, i.e. a list of locks that must be successfully picked to earn points and the belt.
So you can simply look at the required locks for the different belts to find a good lock.
You can find a list of all belts and their required locks online at https://lpubelts.com.