Attack / kills ?

Before you start to see kills in a city, you'll have to fill that person's hospital capacity. On top of that, there's a garrison capacity which has a minimum of 5,000 troops and can be upgraded through research.
Until you injure enough troops to fill their hospital, you won't see kills.

Node hits will get you them though (resource nodes, like gathering gold, food or ore or from gem nodes)

Have the person you're attacking have at least more than their garrison cap, and also more than their hospital cap if you want to see kills.

And an easy way to also get kills is if they have Realm Wrath (Battle Fury) or your clan does a successful rally on them.

So basically, find a bigger target...and hit them enough to fill their hospital. Once all those hospital beds fill up, all the troops who would have been injured troops will now be dead troops.