[kosievdmerwe]

AFAIK controlling shareholder means that the shareholder has more than 50% of the voting power. They or the group they belong to have unilateral control of the company barring some restrictions.

Though looking at this a large but not 50%+ stake can also be "controlling": https://www.upcounsel.com/controlling-shareholder

But controlling looks to more about how much voting power and influence you have rather than how many shares, because remember companies can have different classes of shares.