The alt-win condition feel combined with its sheer power rubbed some the wrong way, while others immediately latched onto it and embraced it wholeheartedly, with Standard, Modern, and Legacy decks fully devoted to taking advantage of the mechanic
Gruul is known for its big creatures and trampling through to deal a lot of damage
Yes, these are corner cases and I doubt they are even more powerful compared to the more obvious options you can abuse, like extra turn spells
One of the best options is Acolyte of Bahamut, which lets you discount Dragon spells since Dragons have a lot of attack triggers and Karlach provides extra combat steps
Look at YuGiOh Master Duel data transfer
It's quite difficult to obtain, especially in pristine condition