There’s 3 ways you can basically use VP.
1 - Setup combos, like apoc, ring, mosh…
2 - Setup your own combos. You know, you go in post 16 with W/E + Q + AA and get out, wait a big, go in with vorpal + Q and VP. You wait a bit for the Q cd back, drop VP + Q again and that basically one shots backliners without them doing anything. With this make sure to get the Q cdr at 16.
3 - You can just VP half their team and while your team focus on killing another hero. Ex: Team goes in hard on someone, you VP the healer + another person in the backline and now your team has the time to finish the kill. This is probably the most important way to use VP.
And, you know, there’s always those tricks you can do with it, like using on your own team to deny damage/pyro/salvo and others, deny damage to structures etc.