(suggested by @conflictedcontradiction)
I won’t lie, I have a personal hatred of this card. Craterhoof Behemoth is, in my opinion, one of the easiest and least interesting ways to win with a green deck in EDH, which is frustrating because so often that’s what he does.
Green likes creatures, and big ones at that. It also likes mana dorks and other small utility creatures like Fauna Shaman and Reclamation Sage. Long story short, Green likes to have a big board full of creatures. Add in cards like Avenger of Zendikar which make a wide board all by themselves, and you have a very likely situation where Craterhoof just outright wins the game. And that’s where the issue in the card lies.
Every card in Magic is working towards one goal: to get their player to win. My issue arises with cards that do this much too quickly and efficiently, leaving no chance for an actual game to be played. What’s fun about slowly establishing a board back and forth, and suddenly your opponent plays Craterhoof and kills you? It’s not a real game and it doesn’t take some absurd effort. It doesn’t have the feeling of a hard fought game, of a well earned victory or a glorious defeat. It’s the kind of game that you shrug off and say “yep, Craterhoof again. maybe next game.” You don’t think fondly on games lost to Craterhoof because the card is so individually powerful without any sort of real setup that it’s not interesting to lose to after the first time.
In addition to the unfun game aspects of Craterhoof, there’s also the deck building aspects that make it aggravating. A deck that runs Craterhoof almost certainly also runs Avenger of Zendikar, a one-two punch that’s sure to win most games. And these decks always, ALWAYS have some way to find Craterhoof. Worldly Tutor, Tooth and Nail, Primal Command. Green has no shortage of creature tutors, and that’s perfectly fine. But Craterhoof is the type of card that makes tutors boring. I see tutors as a way to find a good answer that gets you out of a tight situation; too often you can just find Craterhoof and kill your opponent. So many decks that include the behemoth devolve to have a plan of essentially “play random creatures and then eventually find Craterhoof and win.” It’s boring. You could have an extremely interesting tokens deck, maybe Hazezon Tamar with Epic Struggle and Warrior Tribal. But if you decide to run Craterhoof, you’ll a lot of the time find that you could just cast it and win, which prompts you to make boring games that end the same way.
Finally, Craterhoof is hard to deal with because only a counterspell stops the actual game-ending effect. On a board of five creatures, killing the Craterhoof does practically nothing. You have to be able to deal with most of the creatures or else you die, and if you’re in a position to do that then the creatures should be dead already. And seriously, did it have to have haste? Craterhoof utterly demolishes board stalls, can only be effectively dealt with by counterspells or instant speed board wipes, and in most cases may as well be an eight mana card that just says “if you control five or more creatures, you win the game.” Its only saving grace is that it requires that threshold; when the board is repeatedly wiped and contained, it’s not as big of an issue. But that’s a small comfort.
Craterhoof is a too-often used card that promotes lazy deck building and boring games; it ends games the same way much too often and doesn’t create an enjoyable experience. The most fun way to lose to Craterhoof is spectacularly; see how low your life total can get. All in all this card is a monster that doesn’t promote good gameplay both before and after a game starts, and has become a scourge of EDH.