OK first of all and easiest you can do it with **Sniper** lvl 7. His range is bigger than fountain range and you could easily do it as long as nobody is bothering you.

There is no other range hero who can destroy it solo.

For melee heroes, easiest way is to buy vladimir's offering as it grants lifesteal from the fountain.

**Leoric** is best suited for this as your passive lifesteal works on fountain so you won't even need vladi, just damage. Though with vladi is very very easy.

**Rikimaru** is probably in top 3 due to the 75% miss from smoke. Just get butterfly and some rapiers and you should do it. Attack until 30%, smoke, you will be almost full and then repeat.

Last one which worked for me is **Faceless Void**, although he is a little harder as chronosfere doesn't work on fountain. Passive skill for damage block and a butterfly, full rapier should do it.

EDIT: If you are not that selfish bring on a Crystal Maiden with you. She can cube the fountain making it easy to kill with any hero.

Well, these are just some examples that worked for me. Hope this helps.