Palu has the same ability as the phantoms from Judgement, meaning that you can make him nearly immortal. and with access to green, buffing is not a big deal (aside from end of turn things like giant growth, you can use things like Blanchwood armor.)
To me it reads like the prevention only takes place if there are any counters on him. So if he is artificially buffed, he will stay alive once. Then you have to put more counters on him to get the damage prevention reset. This can be done easily in green, but there are still extra steps to keeping him alive once he is out of counters.
I think the RB Giant could be a good Voltron/Control commander. He comes out early(ish) and limits your opponents hand size so they have more trouble interacting with you. Add some looting, equipment, extra combat, and double strike and he can come out repeatedly and really put a hurt on opponents available cards while swinging for commander damage. Control decks like cycling through cards, and with your commander only ever costing 4 mana, plenty of open mana for action and looting.