Chase hickey?

You can also press Circle (B on 360) to tackle him.

He will just run the same pattern learn the pattern and there is a place where u can run directly infront him and spam your tackle button if not u will be shove by him so holding on the run and shove button will be usefull

Tackling is the answer. I spent a while on this too, but I knew what to do. I just couldn't do the bonus objective. I finally got it when Hickey got stuck on a pillar in the market lol

I would NOT suggest tackling him. When I tackled him, it counted as failing the 100% sync option even though I didn't touch anyone else. Poison darts are also a bad idea because he WILL be counted as dying if the dart take full effect, and rope darts generally lead to accidental assassination if you don't let up quickly enough.

What worked for me was shortcutting through a couple alleys to get ahead of him and then doing an unarmed aerial assassination onto his head. If you run left down the road instead of trying to chase him through the brick marketplace structure, you can get to a nearby intersection before he does. Then you can scamper up a building or just hop on the nearby table and, if you just have your bare fists selected, you can do a flying jump attack to take him down without tackling him or killing him.

I chased the guy for ages thinking he would eventually stop >.<

I agree this sequence was ridiculous. It was extremely unclear as to what you had to do with him, so my first notion obviously was to assassinate him but that wasn't the case here. Eventually after my fifth or sixth run of trying not to shove anyone, I basically said screw it and didn't care about full synchronization at that point.