Market Maker (MM)
brokers provide their own liquidity and are the only counterparty to clients' orders. Transactions are then settled within the so-called internal book. There are also hybrid models
in which the broker transfers part of the clients' transactions to the liquidity provider. This type of broker tries to "get rid of" profitable investors by sending their orders to an external entity. So if you happen to make money, the broker probably has its eye on you!
Although I have my doubts, I think it is possible to find an honest MM broker; but unfortunately, honesty is often difficult to prove before the event. MM brokers have access to certain tools that allow for increased slippage, can set minimum stop loss level intervals, or interfere with client transactions in many other ways.