Evil megas: why all of them of course
But the BAD of the BAD got to be:
Aztechnology: Blood magic, provoking wars, being a bad neighbour etc.
Renraku & Mitsuhama: Both these Japanese megacorps are racist aholes(especially Renraku).
Saeder Krupp: Constantly scheming, One of the most hated megas.
Mitsuhama is worse than Renraku. Renraku was bad under Huang, but thats about it. Most of the time they are too conservative (in business behaviour that is) and constant to be activelky evil. Mitsuhama, OTOH, was basically the main pillar of the Japanese occupation of the Philipines, churns out all that military and propaganda stuff, and has Yak connections. As far as Japanocorps go, Renraku is actually decent. Well, there was the Arcology thing, but, eh...
As for Atztechnology, theyre more openly brutal. Theyd have immidatly killed her I think, so that may not be the best option.
As far as AA corps go, may I suggest Proteus? Heavy into biotech, very ruthless and carless about human life (picking up people off the street to abuse them in their catastrophe situation simulator for example), and very, VERY secretive... of course, downside is, like with Atztech in that case she might already be dead.
As for Evo, they and Horizon are built up as the "good" megacorps. I must say I hate that. I understand its probably just very good PR, but if there is nothing breaking through the appearance, what is the difference between appearance and substance then? Actually for that reason Evo and Horizon might be excellent choices, just to break the clichee heh.