Do you mean "too difficult" or "too bigger punishment"? Either way, I disagree. If they reap the reward of huge salaries, they ought to take some of the risks.
Guilt by association is not acceptable in a first world country. You don't go to jail if your brother commits a crime, you shouldn't go to jail if your company commits a crime. You only go to jail if you commit a crime.
Staw man. The only way that is comparable is if you oversaw your brothers career and received part of his income... if he then committed a crime (from which you benefited), then yes, you could be held part accountable.
Execs are not merely "associated", they are responsible and receive excessive compensation directly derived from the actions of the organisation they oversee. If a corporate crime is committed on their watch they could be held accountable, if not through direct involvement, through negligence - allowing it to take place by not exerting enough oversight or management... to say otherwise would be similar to allowing people to drive cars negligently killing people without consequence, the analogy is not exact, since the car (the organisation) is not purely mechanical and has some degree of autonomy which is where these matters are not cut and dry, and those would be the finer points of a case exploring whether an individual subverted reasonable oversight or not - in the inexact analogy you could say, whether one of the wheels decided to ignore instructions, or whether the driver (exec) wasn't event bothering to steer.
The cost of going after those companies is ridiculous already, once they are proven guilty, it would be simpler if we could punish the company as a person, than to find a real person to punish. After all, companies are very happy to be persons for other legal purposes.
Make it illegal not to have a "custody trace" of how a decision came to be. Even if the CEO came up with it in the shower, for the thing to be implemented, it has to come across a lot of individuals. Make them having to keep all of that data around, and required to disclose how something came to be in case it's revealed as unlawful.
No, what should instead be done is prevent the existence of these megacorporations which have disproportionate influence on humanity in the first place. Prevent them to form and chop up the existing ones aggressively into smaller ones.