Well, I just said Iron Tail to point out it's versatility. Not that I would ever use it. Uhm...As someone who uses Ice quite a lot, I have to disagree with a lot of this. You pointed out a lot of its flaws yourself, with its absolutely horrible defensive typing and its awful Speed. As a tinier nitpick, Mega Abomasnow actually has 7 weaknesses, not 5, but on to the real point. Ice teams already have a good matchup against Water without Mega Abomasnow thanks to Alolan Ninetales, Kyurem-Black, and Lapras. In fact, 2 of the Pokemon listed are staple picks regardless, so why is Mega Abomasnow's usefulness in this matchup even relevant? The same can also apply to the Ground matchup. Here's what I found to be the worst part of your argument:
First of all, Iron Tail is awful coverage on Mega Abomasnow, and there is quite literally no reason to ever have it. Next, what was the point of bringing up Synthesis at all? It's directly counter-intuitive with hail, making you heal significantly less. As a hail setter, Alolan Ninetales has pretty much made every single other Snow Warning Pokemon obselete with its great Speed tier, part Fairy typing, and Aurora Veil in particular. And as mentioned before, Alolan Ninetales is already a staple pick on Ice team. Honestly, if you have a hail team, Ice's best bet is going with no mega at all, since both of its existing megas are lackluster at best.
Speaking of its megas, Mega Glalie actually possesses more desirable traits than Mega Abomasnow does. Its decent 100 Speed tier is appreciated, as well as having access to decent Spikes utility. Despite how Froslass is generally better as a Spiker, Mega Glalie has the offensive presence to force many things out in order to grant it setup opportunities, and can blow up with Explosion as a means of preventing Rapid Spinners/Defoggers. And yes, its Earthquake is weaker than Mega Abomasnow, but unlike Mega Abomasnow, it can actually outspeed and deal with some of the main threats that Earthquake is supposed to hit, specifically Heatran, Magnezone, and Alolan Marowak, all of which are capable of outspeeding and simply KOing Mega Abomasnow before it even gets the chance to attack. When comparing Mega Abomasnow to Mega Glalie, there is hardly any point in listing an example of a Pokemon that they both beat. What exactly was the point of bringing up Garchomp? All it proved is that both megas are capable of KOing a faster threat with a priority move, not showing at all how one would be better than the other.
As Eien said earlier in the thread, the VR is about relativity. Is Mega Abomasnow as good as the Pokemon in the B rank you nominated it for? Walrein and Rotom-Frost serve as Mega Scizor checks, which is undeniably important for Ice teams. Additionally, Walrein has access to Water STAB and the ability Thick Fat, essentially granting it a Fire resistance. Rotom-Frost has Will-O-Wisp utility as well as Volt Switch in order to generate momentum for Ice teams. And for Froslass, it offers a Fighting immunity, and great utility as a hazard lead with Spikes, Taunt, and Destiny Bond, making it a decent choice for hyper offensive teams. All of these Pokemon are much better than Mega Abomasnow, so it wouldn't make sense to put it in the same rank. As for the C rank Pokemon, Aurorus is yet another Snow Warning Pokemon that can also compress an essential role as a Stealth Rocker, while having access to decent utility in Encore and Thunder Wave as well as access to Rock STAB to aid in the Fire matchup. Cryogonal is a more specially defensive Rapid Spinner that also has some salvageable Knock Off utility. And I already went into detail before about how Mega Glalie is better than Mega Abomasnow. Overall, I'd say D rank is a much more appropriate place for Mega Abomasnow.
But maybe I should've emphasized the point that it sets Hail too. Because chip damage is something a typing like Ice really appreciates.
And yes, Mega Glalie does have a good speed stat which would give him more offensive presence on a team, but it's not really versatile. Okay, it's got spikes to set up. But sets that are more creative than Return/Ice Shard/Explosion/Earthquake (or one of these Spikes) don't exist. Mega Glalie is completely predictable. Personally, I've seen that Explosion coming without having to think too much. A Protect later and you have ruined your mon. But that's situational.
Actually, I use Mega Abomasnow on my own team based on weather, and I really felt like it fit on my team, so I decided to stand up for it here when I saw it was unranked.
You're right about the types: I feel like an ass for overlooking Bug and Poison. I'm going to change that.
Reading your arguments made my fighting spirit fade slowly, and somehow my Abomasnow-fan-ness has given in to your "No B-tier" talk.
As I just mentioned, I play with a weather team, so maybe Mega Abomasnow is indeed better than Mega Glalie for my team. Somehow I started to think it would be better than Mega Glalie in general, which it might actually not be, correction; which it isn't. Mega Glalie fits the role of a Mega better in general, and once you get Mega Glalie, you won't be able to choose Mega Abomasnow. I still want to mention Mega Glalie's underwhelming non-STAB power. As it's a single type, it has just one STAB, which does hit hard as well as neutral as well as super effective, outside of that it doesn't really deal damage.
Also, having a Grass type on your team is always handy against Water.
You compare Aurorus and Cryogonal with it. But I don't think that these mon fill the same roles. While Mega Abomasnow goes farther than utility (partially because it lacks utility), the other mon have barely any offensive presence except for Freeze-dry against water teams if you like that. Mega Abomasnow sets Hail as a nice add, but I don't use it as my main hail setter because it can't carry Icy Rock (and I need that to start sweeping with my ace, Alolan Sandslash). I use it sometimes for that purpose when my main is down or something.
Let's see what these viability guys are gonna do...
The stuff about Synthesis: I was doubting about it because I knew it was affected by weather conditions, but I forgot it healed only 33% in Hail. So it's indeed crap. Forgive me. I'm just a pokémon fan, but I'm not that much of a Pokémon pro. But I still want to contribute to Smogon somehow, given how awesome this whole community is.