noun
aggressor
uh-GRES-er/əˈɡresər/
A person, group, or country that starts an attack or conflict.
The aggressor shoves the other man, who retreats defensively.

Etymology
Stepping toward people could mean approaching them, but also attacking them. The agent ending makes an aggressor the one who takes that hostile initiative.
In context
look like the aggressor against people who refused to strike back.
More examples
- Witnesses disagreed about who had been the aggressor.
- The smaller country sought help against the invading aggressor.
- The treaty promised a joint response to future aggressors.
Forms
aggressor · aggressors
aggression noun — Hostile action directed against another.
Similar words
- attacker
- Describes someone carrying out an attack, not necessarily initiating conflict.
- instigator
- Starts trouble but need not personally attack anyone.