Large corporations are definitely being subject to *unjust* exercise of authority. "Hardship" on a corporation doesn't really apply at the scale of very large corporations because the "hardship" is spread out among the many, many shareholders and stakeholders of the successful company; of course, it's not to be seen - it's a relatively successfully company being attacked, in comparison to non-successful companies not being attacked, so hardship isn't to be seen - but the unjustment is still completely there.
The relevant regulatory authorities at national and European level decided that the company had breached the law of the land and applied the appropriate fine based on that law. Would you agree with that?
It's fair to take issue with the GDPR itself, or how e.g. the people working at the Irish DPC are selected or something like that. While I have sympathy for criticisms of the system, these are free democratic entities which rule by consent (rather that tyranny) and they're applying law that was written by a great many people across many legitimate institutions. That looks like "justice" to me, unless you feel it contravenes some natural law. If you think it does this, please explain the relevant principle under which you find the fine unjust.