The spy's sapper can be a fairly decent fair to disable a large group of robots, though usually only have to leveling it up. It's also great for holding targets still for back-stabs.
The only problem is that when a spy saps a large robot, that robot will not stop moving or even attacking. The large robot does seem to visually glitch a little, you can see the sparking sapper, for instance, and the robot tends to bend over a little...(lol)
What effects does a sapper have on a large robot?
Does the sapper have any effects other than temporarily disabling a small robot and his allies?