The first generation of Pokémon games gave players access to 150 monsters and a wide range of tactical options in combat, but there were several features that are now game staples that were not yet there. For example, all moves of each Typing were either Physical or Special. Also, Speed's Critical Hit chance was determined by a set percentage.
Most importantly, though, Pokémon in Red and Blue lacked abilities. These unique features were later added in generation 3 and have remained a core part of the games since. While some affect gameplay out of battle and others actually hinder the Pokémon that has them, others are powerful tools that can swing the results of combat.
Magic Bounce
Field hazards like Stealth Rock, Spikes, and Toxic Spikes are common elements in the competitive Pokémon meta, and trainers who can't deal with them can have difficulty winning. One way is to remove them with Rapid Spin, but Magic Bounce can turn the tide and give the an advantage.
Magic Bounce not only reflects entry hazards back to the side of the field that they came from, but it also bounces status conditions and stat changes. It can be surprising for an opponent to use a move like Thunderwave or Will-O-Wisp only to waste the turn hurting their own team.
Unaware
Many Pokémon like to use moves that boost their stats, and once they're increased, they can be complicated to deal with. Boosted sweepers can KO an entire enemy team, and strong defensive monsters can stall out almost anyone. Moves like Dragon Tail or Roar can force enemies to switch out and reset their stats, but these can be predicted and sometimes played around.
Unaware acts like a safety net against opposing boosts by allowing the possessor to ignore all stat changes on their opponent. This can enable them to unexpectedly tank a strong hit or deal more damage than expected.
Adaptability
In the Pokémon franchise, combatants gain a bonus for using moves that they share typing with. This benefit is called STAB, or Same Type Attack Bonus, and it adds a 1.5x multiplier to the attack's damage. Adaptability takes this multiplier and increases it up to 2x.
The extra 50 percent damage can significantly impact battles and often differentiates between an opponent surviving or being knocked out from an attack. Crawdaunt and Porygon-Z are the two most potent attackers with Adaptability and will want to use as many same-type attacks as possible.
Drizzle
Most competitive Pokémon teams have a balance of Physical and Special Attackers and Defenders to handle various opposing threats, but some trainers choose to utilize unique strategies such as weather conditions to achieve victory.
Drizzle summons Rain for five turns, which makes many of the best Water-type Pokémon even stronger. Rain increases the damage of Water moves by 50 percent and lowers Fire moves by the same amount. Rain Dish and Swift Swim synergize with Drizzle by healing Pokémon and increasing their Speed, respectively.
Gorilla Tactics
Choice Bands, Choice Scarfs, and Choice Specs are all extremely popular held items in the Pokémon franchise that increase the holder's Attack, Speed, and Special Attack, respectively. Their drawback is that they lock Pokémon into the first move they use (until they switch out), but each still sees tremendous use.
Gorilla Tactics does the exact same thing as a Choice Band, raising Attack and locking moves. However, Pokémon with this ability can also hold another choice item to either increase another stat or raise their Attack even further. Galarian Darmanitan, one of the strongest dual-type Ice Pokémon, is the only monster with access to this ability.
Guts
Status moves are a common way to disrupt enemy gameplans in Pokémon battles, and Guts is a great counter to this setback. Guts doubles a Pokémon's Attack stat when it is affected by a special condition. Furthermore, Guts ignores the Attack stat loss from Burn.
A common strategy is to give an offensive fighter like Machamp or Conkeldurr a Flame Orb to auto-inflict Burn and raise Attack. A side benefit is that once Burned, no other status effects except Confusion can be applied. Strangely, Guts doesn't work if the possessor is Frozen and uses a thawing attack.
Multiscale
Multiscale is a powerful Pokémon ability that halves the damage that its possessor receives from attacks. The catch is that it only works while the Pokémon is at full health. Despite this drawback, Multiscale has tremendous competitive viability.
It's flexible, and it can be used to tank a super-effective hit or spend a turn using a status or stat-boosting move. If a Pokémon with Multiscale heals back to full health after taking a hit, the ability will reduce damage again. Multiscale is only currently available to Dragonite and Lugia.
Huge Power
Huge Power is an ability that was first added to the Pokémon franchise in the third generation games, and it's remained one of the strongest. In battle, Huge Power doubles the Attack of the Pokémon that has it.
Huge Power is partially balanced by not being given to any of the Pokémon with the highest attack stat, but creatures like Azumarril and Diggersby can be extremely tough to stand up against with their boosted attack damage. Pure Power is another ability with the exact same effect that is unique to the Medicham evolutionary line.
Shadow Tag
Switching Pokémon to maintain beneficial weaknesses and resistances in battle is an essential part of any trainer's skill set, but monsters with Shadow Tag can almost always ensure that they keep the matchup they want. The move's in-game description says that a Pokémon with Shadow Tag "steps on the opposing Pokémon's shadow," but the mechanical function is that it stops opponents from fleeing or switching out.
Mega Gengar was one of the best designed Mega Evolutions, and it was also the strongest Shadow Tag . Now, with Mega Evolutions no longer part of the franchise, the most notable is Gothitelle.
Protean
Most starting Pokémon possess the relatively disappointing Torrent, Overgrow, and Blaze abilities, but some have access to much more impressive secondary or hidden options. Greninja is one such Pokémon, and its competitive viability skyrocketed when it gained Protean.
This ability changes the type of a Pokémon to match whichever type of move it's using. The benefit of this is twofold; it allows Pokémon to get a STAB bonus every time it uses a move and lets trainers play around with weaknesses and resistances. While Greninja is the most popular monster with Protean, Kecleon can also have it.
