people give api key to portfolio management apps all the time 
Mostly only api keys which allow to view the trading history.
There were indeed some apps which required an API key which allows trading.
And it has been exploited for exactly what i have described, leading to thousands of people losing their funds.
You wouldn't be the first scammer using this technique.
My bot only trades XBT market, if the user sees a shitcoin trade then something is very wrong.
Of course something is wrong then, because this would mean you scammed them and stole their money.
Also why wouldn't i be reputable at all? do i have negative feedbacks?
Because you are posting from a member account. They are being traded here on the forum for a few bucks all the time.
Is that hard to understand that if my payment is only on profits i have no interest but to grow the client capital?
Why don't you simply get rich silently with your super secret magic trading bot ?