Set him down in front of Doom and let him rip and tear. It’s the only way to go.
I really do think a total war game might do the trick.
Into the Breach.
Easy UI, puzzle based scenario, no multiple layers to keep track off, unlike something like Civ for example, and it’s over quite quickly.
Also, slay the spite, although that can be quite rng dependent. Into the Breach doesn’t have much randomness.
I will now read all the following messages.
Edit:
The first Age of Wonders is pretty easy to pick up. Very simple mechanics, easy on the eye and will run on anything.
I think I had this at one point, one my previous Kindle.
Quoted for truth!
It’s a true classic, as far as I’m concerned. Now the only versions you can get on mobile are the free-to-play ones (thanks, EA). Get the original on Steam for $5 and enjoy!
Why not start him with Chess.com? Puzzles, Lessons, Daily games, longer time control games, there are lots of ways to ease into playing. Then once he’s comfortable playing on the PC, maybe he’ll be willing to try other games.
Stuff like Crazyhouse or 3-check could be gateways to more variants of different sorts.
Then you could show him something like Chaos Reborn or Frozen Synapse or even Hearthstone or something similar.
You know aow planetfall is dense and it is complicated but --its starts out sorta smooth. Plus it looks great. And it has that strategy/tactic overlay. I dunno…. we are all home atm so what the heck.
BTw since I am now at home to stay I plan on trying “Breach” tomorrow. That is an acceptable strategy game I am thinking.
Turns out he refuses to connect his laptop to the internet because “there are too many bad things on there.” 
Well, he’s not wrong about that.
Turns out from listening to you talk, he may be one of them 
GOG would seem to be a good solution. Download a game for him and transfer it to his PC via a USB thumb drive and install. Good to go and no internet connection.
That’s a good idea. I’ll look into that.
And they got Big Race USA, my dad’s favourite on computers.
I mean, many of the greatest strategy games of all time (of all time!) are on GoG. You can’t go wrong on there!
I was hoping for Civ V Complete there but I don’t see it.
Go with Civ III Complete? $6
Civ III is quite hardcore though.
No, GOG doesn’t have Civ 5 (yet). They do have Civ3, Civ4 and Alpha Centauri, as well as both of the XCOMs (and all the older X-COMs, too).
Oh, I had no idea they hosted Civ 4. Windows only though — Comprehensible, since I think it can only run, after tweaking, up to OS X 10.11 or something, but still a bit sad.