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Ash kill Pikachu because Pikachu is useless.
Pikachu Snivy Oshawott Tepig Mamepato
Ash's Pikachu will not evolve because Pikachu chose to stay with Ash and gain more experience and in the episode that Ash had battled Lt. Surge Nurse Joy gave Ash a Thunderstone but pikachu don't want to evolve and Brock said that pikachu has more speed than Raichu
Ash has the strongest Pikachu I do too.
If you're talking about Ash's Pikachu then yes, Pikachu is a boy.A Pikachu can be a girl or a boy, but referred as an "it" in many of the games and in the Anime. Ash's Pikachu is a male, for his tail does not have a notch in the side.