After you confirmed that you would like to deploy a package, tasks will be generated and the deployer will start to work on target computers. Stopping a running deployment is not currently possible as this might cause severe issues on target computers.
The only possibility might be - if not all client computers already received the package - that you open services.msc on your Lansweeper server(s) and restart Lansweeper service. This will clear all current deployment data. Of course you should ensure that you remove unwanted schedules from
Deployment\Schedules on the web console.
On the client computers which already received the package, there will be placed an executable under
C:\Windows\LSDeployment and registry entries will be saved under
HKEY_LOCAL_MACHINE\Software\lansweeper\Remote deployment. You might be able to start the computers in safe mode and remove these.