you'll get high leverage with offshore brokers only and the point that you mentioned 'I heard some brokers have banned accounts/blocked money/issues before.' happens because the broker lacks a watch dog. it is always best to go for brokers with strong regulation to avoid such scenarios. if you're based out of europe: i then i think Fxpro, XM, Fxview, ICM would be good options, with 30x leverage.
You’ve got yourself plenty of options. Turnkey forex, Oanda, XTB, Cityindex to name a few. They all are good high leverage brokers. The leverage that they offer depends mostly on the kind of account you hold, and sometimes on the capital that you have invested. Besides high leverage, there are some brokers who offer low spreads as well. Oanda and Turnkey forex are two brokers you could look further into.
Below are the best brokers with high leverage and low margins: Hotforex Alpari FxView FXTM
Always be careful, because low margins tend to provide an excellent opportunity to make some profits, but also creates a possibility to take huge losses to wipe out your trading account in just a fraction of seconds. Choosing a broker wisely as losing can never be a fun thing to experience. Good Luck!