Etherium. But... I sell it to early )))))) less than 50 dollars ))) But still have good income.
Also on bitcoin had about 4x income.
Now invested in few alts just for long-term. So hope in future will have new best investment!

I bought ethereum for $16, got 60% stolen and sold 40% when the price was $300. I know eth may grow up more but after losing most of it I didn't feel like storing the coin. Plus I needed money to throw a birthday party, so I just sold it. It is my highest profit anyway. I got my investment multiplied by 6.
Best investment - NEO
Biggest expectations - Waves
I saw NEO worth $15, watched a video that convinced me of its potential but still didn't buy any! Now I'm waiting till the price drops nicely, so that I could still invest in it.