In general, I think, that the most rememberable BBEGs are the ones which are not inherently evil but the ones that have good motivations but have to make sacrifices when implementing a plan. But that can be sometimes hard to pull off, you have to somehow show the players the real motivation, and the twist has to be understandable/relatable without getting too deep into RL.
What I can offer you right now is pure evil:
Anarchists want runners to steal a prototype chicken breed that some other stolen data shows to be very effective (i.e. resilient to illnesses and high protein meat).
During a run players "accidentally" find data that shows that when green-light from higher ups, the breed will quickly dominate the market. The product is a gem of our BBEG scientist, they are the driving force behind the project.
The twist: it needs to be fed the corp-engineered feed. Otherwise the breed is much less effective. A subscription basically. If you want to try to not have a pure evil BBEG, maybe they are traumatized after a big hunger somewhere in the past and simply do not see other way to solve the "gene trigger" mechanic?
Players will get another mission from the group to try to find out why their new chickens are performing worse than the regular ones.
The main lab of the scientist, where the secret formula is kept, is guarded by genetically modified, technomancer/awakened chickens with temper of hungry piranha sharks.
What will the players do after learning the truth? Sabotage the lab? Hack the report the higher ups skim through to give the final go? Hack the lab so the data that go into production is false? Kill the BBEG? Show him the truth?
Or maybe the scientist wants well but some bean pusher found a way to convince them to put the dietary requirement in place and they are the real BBEG? They only want to boost income so they can outperform the other branch because head of that branch has a better looking business card (something petty).