Blaziken is a fire type Pokémon that belonged to May.
In the beginning of Pokemon Advanced, Torchic was very inexperienced and unsure of itself. It was also curious and very ditzy, also tending to walk around aimlessly wherever May brought it out while also unwilling to listen to May's instructions due to Torchic preferring to do its own thing. In dangerous situations, Torchic often panicked and was also usually crying as well due to its fear.
But when May began ignoring Torchic, favoring both May's Beautifly and Skitty, both of whom she used in her Contests, this prompted Torchic to change. It grew more determined to prove itself to her and ultimately regain May's attention with its competitive streak and need for attention constantly growing as it lost most of its childishness and confusion with this eventually triggering Torchic's evolution into Combusken while learning both Fire Spin and Sky Uppercut.
Upon evolving, Combusken became more assertive and confident in itself and its abilities with Combusken even gaining the confidence to stand up against any Pokemon that had taken advantage of it in the past, including Ash's Corphish. Combusken for a period acted highly aggressive but this later passed due to the fact that Combusken feeling that it didn't need to fight for May's attention anymore.
Upon evolving into Blaziken, it is an adept battler and is also May's strongest Pokémon overall, proving to be very capable in battle as well as in contests.
It has a fondness for Bulk Berries and this was shown when it (as Torchic) had finished up the Bulk Berries of Mr. Big.
The moment it saw May when it came out of it's Pokéball at Professor Birch's lab during which it came over to her out of curiosity then took an instant liking to her Blaziken as a Torchic knew it wanted to be May's partner and friend forever. Whenever they got separated as a Torchic it got worry to point of bursting into tears showing how much it cares for May. After evolving into Combusken and Blaziken it still had its cared and loyalty to May no matter what showing there strong bond for each other.
Advanced Generation series
In AG001: Get the Show on the Road!], Blaziken was given to May by Professor Birch in Littleroot Town when it was still a Torchic. She chose it as her starter Pokémon because she thought Treecko was creepy and scary (though she later called them cute in Trees a Crowd), while the starter Mudkip had attacked her earlier with Water Gun in her face. However, she seemed to like Torchic's appearance and sweet nature.
In There's No Place Like Hoenn, May shows her Torchic to her parents, Caroline and the Gym Leader of Petalburg City, Norman as he compliments that it will be a great Pokémon for her. When Max reacts that May is supposed to choose a Treecko than a Torchic which makes Torchic angrily use Peck on him. After Norman's unofficial Gym battle with Ash, Team Rocket arrives to steal Pikachu and Norman's Vigoroth by using James' Weezing's Smokescreen. They manages to steal Torchic instead of Pikachu. After it being freed by Max, it demonstrates its Ember ability but ends up hurting Max by accident. After Vigoroth defeats Team Rocket's Pokémon and Pikachu was able to blast them off, Norman tells her to take good care of her Pokémon before he gives both Ash and May some badge cases and a PokéNav to Max.
Early on in the journey, Torchic was very inexperienced and ditzy. It did not know how to battle, and tended to wander around obliviously; it also tended to panic when in dangerous situations. On the group's first encounter with Jessie's Seviper (still wild at the time), the Poison-type frightened Torchic by trying to eat it.
Because Torchic was very immature and also lacked any battle experience, May opted to use her May's Beautifly and Skitty instead in battles and contests. However, after the episode AG082: A Shroomish Skirmish, Torchic cries after Corphish steals most of its Pokémon food that causes the two to have a fight by clashing with their Bubble Beam and Ember despite both Brock's Mudkip and Pikachu protest not to cause a fight, Ash's Grovyle stops them with a single Leaf Blade. However, Team Rocket appears to eat Brock's oatmeal after they stole and ate most of the wild Shroomish's apples due to their extreme hunger. Jessie admits they stole its food as they are after by three Breloom who manages to knock everyone with its Mach Punch. Torchic teams up with Corphish until they reunite with Max, Meowth and Pikachu. Upon reaching to both Shroomish and Breloom's territory, they mistaken them for stealing their fruits as Corphish protects it for Breloom's attack. When May and Brock's Mudkip arrived to save the day.
Torchic defends a wounded Corphish as it angrily yells to evolve into Combusken, much to everyone and May's surprise and the arrival of Jessie, James, Ash and Brock. Breloom, which was their leader challenging Combusken in a one on one fight while the latter seriously accepts the challenge. Breloom attempts to attack it with Iron Tail but Combusken retaliates with a Peck on its chest followed by a newly learned Fire Spin. Breloom blocks it with a Mach Punch creating an explosion and Combusken knocks Breloom's face with a newly learned Sky Uppercut. Breloom tells Combusken that no more using techniques but fighting each other using bare hands as both Fighting-type Pokemon exchange their blows with both punches and kicks until they knock each other out as the battle ends with the draw. Both Combusken and Breloom manages to blasts off Team Rocket with their Fire Spin and Mach Punch. Both Pokemon are later show respect each other as they shake hands. Afterwards, when Brock made lunch for everyone including their Pokemon, Corphish attempts to get Combusken's food, but the latter glares at it causing Corphish to back away scared as Combusken and Pikachu gives a hearty laugh.
In Once More With Reeling!, during the break of a Pokémon Contest, Ash and co. were trying to stop Team Rocket from stealing Pikachu and other Pokémon. In the midst of the ensuing battle.
Combusken was weakened which May mistakes of it gotten sick as it evolved into Blaziken, and used a newly learned Blaze Kick to send Team Rocket flying, upon which Ash remarked "would I love to battle you." Afterwards, May used Blaziken in a battle against Sceptile. Although it had a type advantage over Sceptile and its Blaze ability activated at the same time as Sceptile's Overgrow did, the battle ended in a tie and both Ash and May ended up as winners.
Later, it left for Hoenn with the rest of May's Pokémon, along with May herself and Max AG193: Home Is Where The Start Is!
Diamond and Pearl series
Blaziken appeared in DP076: A Full Course Tag Battle!. When it was first called out, Ash seemed to be pleased at seeing it again, and Brock remarked that it had gotten stronger as well. Blaziken was used in the Seven Stars Restaurant tag battle where it the customers had battle and defeat the owners, Roman and Kylie, to be served their delictable food. Blaziken was partnered with Dawn's Piplup and they battled against Roman's Girafarig and Kylie's Drifloon. Together, Blaziken and Piplup defeated the opponents' Pokémon with a Flamethrower and Bubble Beam Water and Fire Whirlwind combination attack .DP076: A Full Course Tag Battle!