One Pokemon from each Gen? Okay.
Gen 1: Hitmonchan - Little Mac Echo. Neutral B cycles through Fire, Ice and Thunder punch, having more knockback and damage, an ice hitbox and multi-hit stun, respectively. Final Smash is Triple Trouble, which summons Hitmonlee and Hitmontop to deliver a combo attack.
Gen 2: Feraligatr - Unique. Heavyweight who mainly fights using bite attacks. Final Smash is Hydro Cannon, where Feraligatr unleashes a blast of water across the screen that drags opponents offscreen.
Gen 3: Blaziken - Captain Falcon Echo. Neutral B is replaced with one of the Mii's customs that's basically Falcon Punch but as a kick. Final Smash is Eruption Kick, where Blaziken Mega evolves and unleashes a series of powerful blazing kicks in an instant.
Gen 4: Ambipom - Unique. Fights using both of its tail-hands, giving them great range and mobility. Final Smash is Double Slap, a devastating series of 100 slaps.
Gen 5: Zoroark - Unique. Illusion is a special allows her to make a copy of herself ala RoA's Forsbrun's Down B, though it cannot damage the opponent. Final Smash is Night Daze, where Zoroark jumps above the stage before crashing down and releasing an AOE darkness attack.
Gen 6: Aegislash - Unique. Stance fighter, Down B is King's Shield, a counter that changes them back to Shield Form, using any attack other than it leaves them in Attack Form. While in Shield Form, they take much less damage and knockback, and their shield is more resistant, but their moves will have added startup since they need to change to Attack Form first to attack. Final Smash is Sacred Sword, a single powerful and unblockable slash.
Gen 7: Mimikyu - Unique. Mimikyu attacks by using its shadow arms as disjoints, giving them range equal to three times its horizontal size. Mimikyu's "head" is invincible so they can only be hit on the main body. Final Smash is Let's Snuggle Forever where Mimikyu captures the opponent inside them before defeating them completely.