How Should We Make This Guy Suffer? Slightly Long, with Cliff's Notes

[Dark_Mace]

tell him you have a business offer that returns 300% profit over 3 years on his initial investment.

Update him peridocially telling him the percentages his money have gained.

At the end of a predetermiend period of time, tell him the company is on the verge of collapse and his intial investment is now back to 0% gain.

Return to him in same manor as he returned your finders fee.