Much easier and quiet way is to find a criminal guy who would kill Skripal for money and make it look like a robbery.
There's no clear reason for Russians to so publicly go after this guy. They gain absolutely nothing from it. Whatever the "message" this was supposed to send, it's unclear.
Large numbers of former KGB and FSB agents live outside Russia. These well-publicised killings send a clear message to them about the consequences of spilling—or threatening to spill—Putin’s beans.
Except that it is our real life and it clearly shown to not be like any tv show before.
This guy lived quietly in the UK and had no "Putin's beans" to spill. He did blow cover of several hundred Russian agents, but he did time for that in Russia and then he was exchanged. It is possible it was a long-delayed payback from the GRU, but, again, there is no reason for it to be made that publicly. He could've choked on a pound coin and everyone who needed to know would've gotten the message. But the way it stands, the only discernible message here is "don't do any more spy exchanges with Russia".
>Rather than merely living an isolated life in retirement, Mr. Skripal, a former Russian military intelligence officer, continued to provide briefings to spies in the Czech Republic and Estonia, according to European officials. Now, it appears he was also active in Spain.
https://www.nytimes.com/2018/09/06/world/europe/skripal-pois...
As well as the well-substantiated conclusion of several international investigations. Same reasoning for Litvinenko’s polonium tea and North Korea’s nerve agent assassination.