For-profit prisons and hospitals.

Using "tipping" as an excuse not to pay workers living wage.

Displaying prices without tax.

P.S. This is illegal where I live, but some places would be better off if it were illegal there also.

Advertisements for prescription medication

Lobbying and lobbyist groups.

Gerrymandering.

One side changes on EULAs.

Hardware that requires a proprietary service to work.

Selling life-saving drugs at large multiples of the cost to manufacture + distribute. The most obvious example being insulin.

Switching political party in the same term that you were elected to office.

CEOs making 100x the median worker at the same company.

Assault rifles and other automatic or military-grade weapons. They have no practical purpose in the hands of a citizen. Pistols, shotguns, and hunting rifles should be sufficient for hunting and self defense.

Generic finance bro bullshit. Frivolous use of bank credit for speculative investment. Predatory lending. Credit default swaps. It's just a spectrum of Ponzi Schemes. Let's reinstate the Glass-Steagall Act.

Non-disclosure of expensive gifts to Supreme Court judges. Looking at you, Clarence.

Military recruiting at high schools.

Junk mail. You literally have to pay a company to stop sending it.

Insider trading by Congress

Landlords. Housing as a commodity in general.

Forced arbitration

Something (almost) no one has mentioned: factory farming of livestock. I'm not gonna say a person who engages in subsistence farming shouldn't be able to keep a coop of chickens for eggs (as long as their chickens are well cared for), but large scale animal husbandry and livestock is devastating to the environment and genuinely cruel.

Churches backing and funding politicians.

Screwing over a large number of people to benefit a small number of people. Religion and corporations immediately come to mind.

Tracking & profiting off it.
Forcing people to be tracked to use a product that they then sell that data should be illegal without your complete, informed consent, and you get to opt out and still use the product.
All tracking should be regulated. You own your personhood 100% and only you can make money off of that.

Forced arbitration

Zero hour contracts in the uk don’t actually have to have an actual contract so if your boss says that something is in your job description you can’t argue otherwise because there was never a contract that said what your job roles were to start with.

Capitalism

EDIT: also i read the other comments and hilarious amount of other things mentioned also boils down to "capitalism" or their illegalisation would basically needed for capitalism to be outlawed too.

Non-utilitized internet service.

Internet providers ARE UTILITIES. Regulate them like one.

payday loans

Let's give an example that is more uplifting.

A 16 year old who just got their motorcycle license being able to buy a 200hp superbike capable of doing 180+mph.

For all intents and purposes, this should be illegal, because the teenager (usually) doesn't have the skills and willpower to handle such a powerful motorcycle as a noob.

But it does feel awesome to be able to buy whatever motorcycle you can afford once you get your license in the US, rather than being forced to start on a 125cc that can't even hit 60mph.

Family vloggers

Smoking. It's literally a drug and causes lots of health issues like increased lung cancer risk, but the worst part is that if someone smokes near you then you also inhale some of the toxins even if you yourself don't smoke. And in my country it's common to see people smoking on the streets. Combine this with air pollution and yikes

Tipping.

Capitalism

Politic lobby.

Capitalism, Literaly all of capitalism.

Ultra bright headlights.

Governments, businesses, corporations and all of us just normalizing and accepting that the majority of everything we own or buy at affordable prices are all based on taking advantage of as many poor people as possible in our home countries and most of the time in third world developing nations where people are paid pennies for their work.

We complain about China, yet everyone buys everything from them. We look down on third world developing countries yet we base our economies on manufacturing a ton of stuff from them because they all hire people for as little as possible. In America, Canada and Europe, we have agricultural workers we ship in from poorer countries to harvest our crops because we don't want to pay higher prices for labour to the people that live in our countries .... we would rather pay poverty wages for imported labour that we don't want to stay in our country.

Everything we do, buy and pay for is all based on exploitation ... our entire economy the world over is based on it ... yet it is perfectly legal ... but if we are all so moral, enlightened and intelligent then it should be illegal.

Killing animals forr pleasure.

Exploiting animals

As a general rule, the amount of exploitation and fraud it takes to "become" a billionaire should probably be illegal.

Lying about what you do with peoples data and who you share it with.

Sentencing and punishment are affected by "caste"

Reposting things from reddit that have been posted there over 1000 times.

Churches.

Religion