The idea of "giving it back" is the problem because you're describing retaliation... and that is often penalized. You're also meeting the opposition on the mismatches they've dictated.
It isn't about hanging on when the other team decides to run you through the boards. Leafs need to build a team and have the ability to dial up and down the physicality, agitation, attrition game based on what they want to achieve, who they want to target and make less effective.
If we use the Florida series as an example, we should be crease crashing and making life tough on Bobrovsky to stay in the game mentally. Wear him out physically with little bumps here and there, heavy traffic, after the whistle play. He's a guy who has dehydration issues. Why are you not making life hard on him? Make it a chore for him to reset after every whistle. From a forechecking POV, we should be running Ekblad, Forsling through the end boards on every puck retrieval, not hacking and slashing back once Gudas has already put a licking on you. By mid series they should be feeling something to make life a little easier. Barkov should be harassed with every puck possession, etc. little slash here and there as he's cutting in, put the body on etc.