Without its ability, Abomasnow would certainly be overlooked by many players. However, it is the only fully evolved Pokemon with Snow Warning, making it a staple on hail teams. Also, since hail is the least common weather, it does get some use on balanced teams as an answer to more dangerous weather conditions.
When you look past its ability, you find a Grass / Ice Pokemon with seven weaknesses and only four resistances. It does have decent Attack and Special Attack which, when coupled with its base 60 Speed, instantly bring Choice Scarf to mind. It has very powerful STAB attacks such as Blizzard and Wood Hammer that can make up for its only decent offenses. When you look at its defenses, they are only average, but when coupled with key resistances to Water-, Grass-, and Electric-type attacks, a specially bulky set can be valuable. Its access to useful support options such as Leech Seed also helps mold defensive sets together. All in all, while Abomasnow may seem controversial, its niche as the only fully evolved auto-hail inducer makes it a fierce competitor on the battlegrounds.
With a Choice Scarf, Abomasnow reaches 354 Speed, allowing it to surprise slower foes such as max Speed Tornadus and revenge kill efficiently. Its STAB Blizzard has perfect accuracy under hail and deals massive damage to any Pokemon that doesn't resist it. Grass Knot is the preferred Grass-type attack because it offers great power against heavy foes and doesn't have recoil, allowing Abomasnow to switch in more times. Hidden Power Fire covers Steel-types, such as Scizor and Ferrothorn, who resist Abomasnow's STAB moves. For the remaining Pokemon such as Heatran and Magnezone, the snowman has Earthquake to destroy them. However, these Pokemon commonly hold Air Balloon, so they will have to suffer some prior damage in order to pop it.
A Hasty nature and 240 Speed EVs allow Abomasnow to outspeed Tornadus by one point without hurting its offenses; max Special Attack maximizes Blizzard's, Grass Knot's, and Hidden Power Fire's damage output; the remaining EVs go into Attack to give Earthquake a small boost. Wood Hammer is an option, as it hits much harder than Grass Knot against lighter opponents. The main reason it isn't recommended is that Abomasnow's health will go down too fast without recovery. If you use Wood Hammer over Grass Knot, switch the EVs to 140 Atk / 128 SpA / 240 Spe, as this provides Abomasnow with enough power to OHKO Swords Dance Scizor with Hidde Power Fire (the most common Scizor variant in this metagame alongside the Choice Band set) if Stealth Rock is on the field. If you prefer a physical Grass STAB but dislike the recoil of Wood Hammer, Seed Bomb can be used instead. However, 60 Base Power is a great difference and may not be worth the lack of recoil.
With a Choice Scarf, Abomasnow can revenge kill many dangerous threats that rely on weather to outspeed the snowman; Venusaur and Shiftry are just a few examples. Although Abomasnow has Earthquake and Hidden Power Fire, it is still a good idea to remove Steel-types via other methods so that Abomasnow can spam Blizzard and Grass Knot more easily. As such, Magnezone is an ideal partner, since it can trap and kill Steel-types without much trouble.
I've seen Abomasnow's online and this one may be the one that the person used, it was pretty strong pokemon
This set takes a completely different approach to the snowman by taking advantage of its decent defenses and typing. As the name suggests, Substitute and Leech Seed are the most important moves. Substitute provides Abomasnow with an immunity to status, while Leech Seed slowly reduces the opponent's health while restoring the snowman's own health. Blizzard is a great move to have on Abomasnow, as it is powerful and a reliable STAB under hail. When Protect is used alongside Substitute and Leech Seed, Abomasnow can be very annoying because Protect allows it to recover the health it loses from creating Substitutes.
A Calm nature and the given EV spread provide Abomasnow with good overall bulk to maximize the snowman's potential against the Grass-, Water-, and Electric-types that it is supposed to stall. Wood Hammer may seem like an odd suggestion, but it gives Abomasnow a strong STAB move for when it isn't behind a Substitute. Focus Punch can be used if Abomasnow's job is to get rid of Tyranitar and the common Steel-types that like to switch in. When running Focus Punch, a Careful nature should be used as it retains Abomasnow's power without losing its bulk. Taking into account the speedy nature of the metagame, Ice Shard has some uses on the last slot, giving Abomasnow some priority to abuse. A Sassy nature can also be used with an EV spread of 252 HP / 4 Def / 252 SpD to allow other weather inducers to outspeed Abomasnow in order to preserve hail while maximizing its special bulk.
As the goal of this set is to stall, entry hazards are a must as Leech Seed tends to cause switches. Toxic Spikes make the opponent's Pokemon suffer increasing damage each turn, and with Substitute and Protect, it will do wonders draining your opponent's health. Forretress, Roserade, and Tentacruel are the best partners to set them up since they have great bulk and, in the latter's case, great synergy with the snowman.
This sounds like a really good way to win and use an Abomasnow in battle
Abomasnow has plenty of STAB moves to choose from. Ice Punch is its strongest physical Ice STAB, but it is inferior to Blizzard. Giga Drain is a possibility for the SubSeed set to restore more health, so it can be used over Protect (Blizzard can't be replaced or Grass-types wall the set completely).
Outside of the sets in this analysis, Abomasnow doesn't pull off anything else as effectively. It can run a physical attacker moveset with Swords Dance, Wood Hammer, Ice Punch, and Earthquake, but it doesn't have the Speed or power to pull this off.
Abomasnow's main counters are Pokemon whose typing allow them to resist its STAB moves; Steel- and Fire-type Pokemon are therefore the best counters. They can come in on even Abomasnow's coverage moves and threaten the snowman out with their STAB moves. Bronzong, Jirachi, Metagross, and Volcarona are great examples of such Pokemon.
If one takes into account the fact that Abomasnow's offenses are only average, bulky walls that aren't hit super effectively by its STABs can come in and set up on it. Blissey is one of the examples; it can come in and, with access to Wish and Flamethrower, threaten the snowman or attempt to outstall it. Chansey can also come in on Abomasnow, but its sub-par Special Attack means that if the snowman sets up a Substitute and avoids Toxic, Chansey can only attempt to outstall Abomasnow.
This is a good Pokemon to use with Hail Team, i had battled someone online with a Hail Team and they were pretty good