)a "good deal of regulations" exist to only drive out competition that's why these large corporations lobby for them to be passed in the first place.

Not necessarily. Anti-trust laws are designed to prevent monopolies from forming. Monopolies, historically, are one of the worst enemies of startup businesses. Far worse than current government regulations. During the Gilded Age, they would engage in a practice called predatory pricing. This is a practice where a well-established monopoly uses its wealth to temporarily lower prices of their product far below the market value, and sell them at a net loss, driving all other competitors out of business. When the competitors were bankrupt, these monopolies would then raise the prices to exorbitant levels and begin cost-cutting, delivering an inferior and far-overpriced product to a consumer that now has no other alternatives.

Monopolies had an arsenal of other tactics for crushing startups, from propaganda to intimidation. During the Gilded Age, some railroad monopolies would even cut off access for their competitors' supply lines and choke the life out of them.

So much for boycotting being an option.

I also disagree because I never believed in being helpless under the mercy of corporations.

This is due to safeguards imposed by U.S. Legislation. There's a book entitled The Jungle by Upton Sinclair, and it's a great piece of literature on this topic. It was a hugely important piece of journalism that led to the writing of the Pure Food and Drug Act as well as the Meat Inspection Act. Here is an excerpt:

[T]he meat would be shoveled into carts, and the man who did the shoveling would not trouble to lift out a rat even when he saw one—there were things that went into the sausage in comparison with which a poisoned rat was a tidbit. There was no place for the men to wash their hands before they ate their dinner, and so they made a practice of washing them in the water that was to be ladled into the sausage. There were the butt-ends of smoked meat, and the scraps of corned beef, and all the odds and ends of the waste of the plants, that would be dumped into old barrels in the cellar and left there. Under the system of rigid economy which the packers enforced, there were some jobs that it only paid to do once in a long time, and among these was the cleaning out of the waste barrels. Every spring they did it; and in the barrels would be dirt and rust and old nails and stale water—and cartload after cartload of it would be taken up and dumped into the hoppers with fresh meat, and sent out to the public’s breakfast.

I'm certain you'd feel a bit more "helpless under the mercy of corporations" if every major meat distribution warehouse took it upon themselves to compromise the safety of their meat just to improve their bottom line.

This excerpt from The Jungle focuses on the widespread mistreatment of workers in industry:

Here was a population, low-class and mostly foreign, hanging always on the verge of starvation, and dependent for its opportunities of life upon the whim of men every bit as brutal and unscrupulous as the old-time slave drivers; under such circumstances immorality was exactly as inevitable, and as prevalent, as it was under the system of chattel slavery. Things that were quite unspeakable went on there in the packing houses all the time, and were taken for granted by everybody; only they did not show, as in the old slavery times, because there was no difference in color between master and slave.

The lack of corporate oppression you take for granted was not always reality. People fought for it. Legislation is what holds it back.

If we stopped buying IPhones Apple is finished and they know that.

But what would it take for people to stop buying iPhones? News about suicides in Apple's overseas assembly plants have little to no impact on their bottom line. As was mentioned in the original post, United Airlines' stocks are at an all-time high. Boycotting is a spectacularly inefficient and ineffective way of controlling corporations because not enough people give a shit to make a financial impact in any given case. Do you think this would magically change if the economy was completely de-regulated?

If there were a news article tomorrow that stated Coca Cola were executing workers in South America, how many people do you think would actually stop drinking Coca Cola? The vast majority of Americans won't even see the news tomorrow.

What about a company that runs a monopoly on a necessity, like toilet paper? They can commit all the atrocities they want, and nobody is going to stop buying toilet paper. What would they do? Use leaves? If they were a sufficiently established monopoly, they could simply crush all competitors and make themselves the ONLY option for buying toilet paper.

Boycotting is an unworkable tactic for preventing companies from committing atrocities.