Definitely a cockerel. Those sickle feathers are very noticeable. But that would have been great if he had been a hen, because i have one named Sophia!
If you want to keep him, I can help you manage him if he turns aggressive. I don't know if Lavender Orpingtons turn aggressive though. I use a method with my rooster that works really well and isn't mean or cruel. Just let me know!
I love my big lavender orpington roo Ash, he's wonderful to his ladies and never aggressive to humans, I encourage you to keep him first above all other roos, you won't be sorry.