Splitting up companies increases the value of the "babies", and doesn't prevent reforming, as with AT&T and Standard Oil.

What about revoking corporate charters and nationalizing?

I'm against capital punishment (due to the possibility of wrongful convictions), but if corporations want to be people, let's start executing them.

Shut 'em down, Uncle Sam takes the assets.

Force the company to issue more shares and give them to the government.