"usually" is the problem.
The Sherman Act also mentions a ceiling of 10 million, 3 years of prison for private persons. And from history we know antitrust authorities broke up companies like AT&T or Standard Oil, which seems to me a much bigger punishment.
Both laws only mention the maximum fine.
Yet you don't see small companies sweating over competition law.
They would if it applied to them and they had to do work to comply. This is very simple. If a law applies to a company, companies will worry about it and the perceived risks. If a law doesn't apply to a company, they won't worry. Ideally, both the laws and their punishments are as narrowly scoped as possible to prevent abuse at the whims of enforcer subjectivity. It goes without saying that a business not affected by a law won't sweat it like they might if affected by a law. Couple that with ambiguities in the legislation and effort to comply and it's clear why small businesses sweat one and not the other. It's a very poor comparison.
Had you read the GDPR you'd knew that punishment is proportional to the offense, had you read the regulation in charge of receiving complaints you'd know that they said they will first give a chance to comply to the law before resorting to punishment. The only ambiguity is in the broad term "legitimate interest" offering exemption to GDPR.