Torchic. Caught it because it was my first ever starter. Leveled it up into Blaziken, one of my favourite Pokémon.
The first Pokémon Buddy I caught here was a Magnemite. It is now a Magneton, though admittedly I don't remember it all that well.
Looking back through my Pokémon Collection, it appears my very first catch was a Venonat, followed by a Gastly! Come to think of it I never got around to evolving Rick Gastly into a Gengar... Oh well.
it was an alolan vulpix that I accidentally evolved into an alolan ninetales therefore requiring me to posts 10 times per level for it to go to level 100 which i am not doing.