The reason South Korea is putting the prominent figure in jail is more a political persecution than union busting. Union busting activity could have been resolved without a jail term.
In Korea the current administration came to power by those powerful unions, so it has to act against Samsung family as they were very close to previous administration. This is one of the avenue to punish them.
If you have any first hand experience dealing with union in South Korea, you will understand why multi-national companies are reluctant to operate, provide services and open manufacturing in that country.
For economy to grow and keeping in welfare of the employees there has to be a balance between corporate and unions. If an employees decides to go on a strike, company cannot fire them, cannot use temporary staff, cannot ask subsidiary or other departments to help, cannot outsource work done by that person to outside company, cannot close that division. If it does any of this its a criminal offense and the person including the CEO can be jailed. The only way to negotiate is to deal with primary union representative carrying industrial action and these union are current government affiliated and their leaders wields political powers. They will come with 145-152 demands to sign an agreement between union and company. But before coming with demands they will make the employees to go on strike to have a better bargaining power (they call it industrial action).
If company do not negotiate in good faith which is determined by the union representatives not by reasonable laws, the company will be punished. If company do not agree to demands the only way out is to close the legal entity. So most multi-national companies try to limit their exposure to those unions and that's the reason they don't invest as much. Most of the Korean economy is driven by local 5-6 billionaire families who themselves wield a lot of political power so can negotiate strongly with those unions.
Funny enough Korea is more socialist than China when it comes to labor reforms and unions. Also in Korea unions wield strong political powers.
In China there is only one union, which is toothless and do not allow strikes to happen. They also have to abide by company laws and rules. Its only labor courts and department which determine whether company laws in handbook are reasonable or not and every employee at least need to comply with the company handbook.