I'm not saying that you're a kid. If you're not an AMXX scripter, you can easily get tricked because you can't know for sure if the plugin you'll receive is any good or if it's really original or stolen.
Just like I guessed - it already exists. This is a part of the StatsX plugin that 90% of servers use. I'm not sure if the default Stats plugin from AMXX has it, but StatsX definitely does - search for it.
It shows all of your victims and attackers + damage dealt/received and number of this on the HUD in the end of each round.
Dear admins. If somehow you managed to read this, plz fix.