Possibly start an online wallet service and "accidentally" leave all company funds in a hot wallet where "hackers" can get at it (this is the most profitable because it requires no startup capital, can operate in your moms basement and works over and over again).
Start an online gambling game where the odds are in your favor. It doesn't even need to be very sophisticated to clean up. Just make it a little less stupid than "rock-paper-scissors" or "guess what number I'm thinking about".
Build up a little rep on this forum and borrow money. Pay back small loans over time then take out one large loan and never pay it back.
Start an ASIC miner manufacturing company and take preorders for equipment with unreal specs. You don't even need to deliver good working equipment with all the parts that live up to your specifications lies. Just make everyone that ordered wait more than a year to get it and they'll be happy if you ship them shit in a box because at least they finally got something from you.
Tell that to the gambling sites and ASIC manufacturers. They think they're running businesses. I do agree with you. They have seriously eroded confidence in Bitcoin in general.
I am honestly not sure how/why ASIC manufacturers are able to get so many people to "invest" in preorders, especially when they have not even proven they even sell real equipment, and have histories of delays