Potential SPOILERS for ARROW SEASON 4.
Everybody thinks its mama Smoak or captain Lance , but I have to tell you something, there are not in the grave.
You are probably wondering Why. well you have to see reaction of three character that are ,,save". You can see that for Oliver it is the hardest and that he is devastating then Felicity she is really sad too but not as much as Oliver. For Barry you can see he is sad but more for Oliver than he is personally sorry for dead character.
What would happened if Lance is dead ?
Then. Instead of Oliver being devastating it would be Laurel for sure and mama Smoke (except her and Lance are break up). And Oliver will be sad just for Laurel and Sara , when she came back. So Laurel will be in front of the grave and crying and probably Felicity would came to her just like Barry came to Oliver. So... no Lance.
What would happened if mama Smoak is dead ?
Same thing but Felicity would not be at the car and i thing she will not ask Oliver to kill somebody for her.
SO WHO COULD THAT BE ?
There are 3 choice for dead man the firs one is :
3.Laurel Lance (Black Canary 2)
2. William (Oliver son)
1. Thea Quinn (Speedy)