Coming up with a unique method of Energy acceleration is really tough. With Treasure Energy being able to attach itself from the Prizes, there's not many ways that you can accelerate Energy that haven't been done before. But I don't believe there has ever been a card that accelerates upon a Pokemon retreating. And when I asked myself what sort of Pokemon thematically could utilize the Energy being thrown away by paying its Retreat Cost, and Garbodor was a natural fit. Garbodor and the discard pile are kinda synonymous with each other, which makes me not want to use it at all, but I can't think of a better Pokemon to show the idea of a Pokemon with an Ability called Trash Collector walking around simply picking up another Pokemon's unwanted Energy and holding onto it to power up its own attacks.
The idea to exclude itself from its own Ability was to prevent it from getting a discount when retreating, but I don't think it's that much of a stretch to say that a Garbodor wouldn't want to pick up its own waste. Sharing your Energy with multiple other Garbodor on your Bench is recommended, though.
The wording for Trash Collector was kind of a nightmare to figure out because I can't just use the word "put" everywhere. It's a little awkward, but I think it's correct.
As for an attack, I also didn't want to go the obvious route of "damage for each Energy" since this card's Ability allows it to stockpile Energy; however, once again, theme won out. The idea of Garbodor the garbage man using all his collected garbage to inflict big pain on the enemy is a great visual. I originally only used Garbodor's Energy for the damage calculation, but I didn't think that it would be strong enough to warrant any use if it did (Garbodor FST actually does 130 for the same cost and it gets no play). Victini V is great in decks that can utilize it, and I think that one-Prizers are criminally weak. So I increased the cost and increased the damage and that did the trick. And yeah, the attack is called Hefty Bomb because of Hefty brand garbage bags. It, like everything else, is also thematic; Garbodor's massive damage for its massive cost can only be described as HEFTY HEFTY HEFTY.
Bottom stats are typical for SWSH Poison-types, and Garbodor in particular. I would have liked to give him a little more HP, but with his damage potential, acceleration Ability, and like 8 other SWSH Garbodor cards with 120 HP, I figured it best not to mess with convention in that regard. Placements are the best I could do by doing what you said. Hope it's good enough.
References: Skaters' Park; Lucky Ice Pop (kinda); exceptions to stuff always goes immediately after the word Pokemon (Zoroark EVS, Abomasnow CRE, etc), so as odd as "this Pokemon, retreats," looks, it's still correct; Victini V for the attack