Kakuna Matata

Kakuna was captured by Abe during the Red Anniversary. It only knew Harden, but was often sent out to battle, resulting in it fainting. It managed to reach level 16 without evolving before it was released in an attempt to withdraw it from the PC.

Lore interpretation
Kakuna was seen as being spiteful that it had been deposited into the PC, swearing revenge unless it was retrieved back into the Party. When attempts to do so resulted in several Pokémon being released, it relented, saying it could wait. When the powerhouse of the team Growleerzard was released, Kakuna was blamed.

It was later shown to have attempted a zero approval gambit: become a hated figure so that its eventual release would clear out any negativity with the run.

Name
Kakuna Matata is a play on the phrase Hakuna Matata, which is Swahili for "No worries". Given the problems that it inadvertently caused, this is rather ironic.