What kills it for me is that the big flier having ward would have been solid on its own, so the ward cost and triggered ability make this vampire brutal
But what sets the RULE work apart is that it's the most variable and unpredictable
But then you're back to being the threat
Ill just point out a few popular cards with 2 retreat cost and up: Buzzwole-GX [c,c,c], Zoroark-GX [c,c], Golisopod-GX [c,c,c], Rayquaza-GX [c,c,c], Lycanroc-GX [c,c]
But, availability might only be in Japan shops
There have been so many busted combo decks making use of Lotus Petal and Lions Eye Diamond, but my favorite will always be what I believe to be the most broken deck in Magic history (at least since the advent of the four-of rule and restricted list), a turn 1 kill deck detailed here , making use of the temporary abusability of Lions Eye Diamond when you could use it to play a spell from your hand before discarding your hand