These days I'm really trying to not ever think in terms of 'wasted slots.' There lies the way of X-23 'what is a Legend?!' conversations. My view, which I really try to hold to, is that every character, every look, and every storyline is SOMEONE's favorite. Every possibility deserves a figure, if that's true, because everyone deserves their favorite thing. And any discussion beyond that is just 'is this serving the needs of the many over the needs of the few' and that's just not a conversation I care to have as someone that loves Shatterstar and Kylun - because that logic means I would never get some of my favorite characters -ever-.
So, to me, a real 'fail' is when they just biff the thing they're trying to do to the point where it's potentially undesirable even to the person that actually wants that character/look.
For example, as a huge Wolverine fan, I think they biffed it with Astonishing, and I still don't own that figure. They finally were close to a good scale on Wolverine, and they went and made a new, awesome Wolverine that was even taller than the last ones that were -okay-, if not perfect, scale-wise. Then they went and did a whole new body for Wolverine in the Gamerverse line and made that one EVEN TALLER. The latter isn't a fail only because it is accurately doing what they intended it to do. It only becomes a fail if they use that body again for future comic Wolverines.
I'd also consider WWII Wolverine a fail because no one seems to know what it is. In this line of figures that are all based on something (comic, video game, cartoon, or movie/TV show), why do we have a random Wolverine figure that doesn't seem directly based on anything? And why does he have like a weird pouty supermodel face?
It seems like a great WWII soldier figure. But it's a -bad- Wolverine figure and you won't convince me otherwise unless you can identify the source. And given all the conversation around that figure was 'where the hell did this come from?' and a bunch of people posting comic images and stuff that aren't actually in line with this... well, good luck.
Staying on my Wolverine kick -- I'd call '97 Logan a fail. It is a crappy action figure on top of failing to do the thing it is trying to do by cheaping out on the legs. So you get very comic book style detailed legs, and a cartoon-style non-detailed jacket, and it fucking looks weird together. In addition to those legs just being kind of shit to begin with and pretty goddamn old at this point. I've sold two ML collections since those legs first showed up on a Logan figure. Terrible figure AND doing a terrible job at interpreting the source material. THAT is a fail.
Silver Centurion IM is another figure I'd call a huge fail because it seemed to disappoint -specifically- the people it was made for. I don't know of any IM fans (
@Akatsuki,
@Resilient - chime in here?) that was happy with that figure. If your Iron Man toy doesn't make Iron Man fans happy.. .you done fucked up.
I'd also consider a LOT of MCU figures fails for no other reason than being developed prior to final designs, so you end up with a bunch of figures that don't even match their movie appearance, which is the whole fucking point of the figure.