Best one vs one(in a 5vs5 game) I'd say Lich/Viper/Visage/Silencer. Lich for the unlimited mana and nova, Viper/Visage/Silencer for the orb effects which the creeps ignore, letting you take shots at the hero.
Best one vs one(in a 1v1 game where you start with 3k+ gold) I'd say tinker. You can't push/farm as good as tinker(with BoT). Late game he becomes a beast too.
"diba IMBA naman kung ung hero mo e killer na, tapos mass farmer, tank and harasser all in one?"
Tinker's a mass farmer/pusher/harasser. Late game he becomes a killer/tanker too. IMBA? Very. Even if you can manage to kill him, he'll still rape your base 10x better than Furion would dream he could.
"50% hero 50% skill ng gumagamit"
Hinde ata, it's more like 90% player skill 10% hero skill. Unless one vs one tapos melee vs range.