Update for Gen 8
Turns out there were multiple.
B2W2
- Starting 11th of January, 2013, and ending the 10th of February, 2013, this Genesect was available. It was in a Cherish Ball and could have any nature. It was available as a Pokemon Center Distribution, and was Japan exclusive:
Genesect
Ability: Download
Level: 50
- Techno Blast
- Magnet Bomb
- Solar Beam
- Signal Beam
- Starting the 13th of July, 2013, and ending 30th of September, 2013, this Genesect was available. It came in a Cherish Ball. It was distributed in Japan at the Mewtwo Awakens Movie Event.
Genesect @ Choice Scarf
Ability: Download
Shiny: Yes
Hasty Nature
- Extreme Speed
- Techno Blast
- Blaze Kick
- Shift Gear
XY/ORAS
- Starting the 1st of November, 2016, and ending the 28th of February, 2017, this Genesect was available as a Serial Code event for Pokemon's 20th anniversary in Europe and America. It came with the blue pentagon mark and in a Cherish Ball, as well as being able to have any nature.
Genesect
Ability: Download
- Techno Blast
- Magnet Bomb
- Solar Beam
- Signal Beam
SwSh
- Starting 20th of November 2020 in Japan, you can receive this Genesect through serial code. It can have any nature and comes in a Cherish Ball.
Genesect
Ability: Download
Level: 60
- Techno Blast
- X-Scissor
- Metal Claw
- Fell Stinger
Source
