Validators slash is executed in the following scenario.
Jailing validator
When double sign evidence is given on the consensus layer, slashing module jail the validator to let the validator not be able to participate in the consensus voting process.
If the validator has staking pool created, system automatically generates ProposalSlashValidator with automatic parameters - offender, staking pool id, misbehaviour time, misbehaviour type, jail percentage, colluders, refutation.
Slashing multistaking pool created by the validator
Once slash validator proposal is created, the validator on the proposal could provide a refutation by sending MsgRefuteSlashingProposal and proposal’s refutation field is automatically updated.
The proposal passes the voting period and users put slash percentages as part of the vote message.
If the proposal pass, the average value of the slash percentage from upvoters is calculated and it’s applied to the pool.
And once pool is slashed, no one can put more deposits on the pool.
It’s a permanent operation and once the pool is slashed, there’s no way to recover it to original status.