POSSIBLE SPOILER: Who is Dante?

I know this post is a few months old but even now, I'm actually still kinda clueless as to who he is. All this time when they said his name I thought they were talking about Sisco's Brother from earth 2. It's like around 2 months ago when you posted this topic the guy's name just popped out of nowhere. I google searched who Dante was on arrow and it just showed me Sisco's brother. So I kept watching the show and still I couldn't make a connection to who this Dante was. It's like an entire episode or scene was missing from the show. Either that or I wasn't paying attention in the first place...