Interesting question from student

Today during one of my Bitcoin courses one student had an interesting question. I was giving the example of what would it mean if 1% of the population would adopt BTC completely (then 0.26 BTC must suffice for a whole lifetime per person on average). The student said this would be horrible, completely glossing over the point I was making, of the value proposition.

So, on a planet with just these 80 million people and all 21 million BTC are mined. Since BTC doesn't solve the unfair distribution problem. And since people are still humans with human emotions including greed and irrational behavior. The question in this scenario is:

What would prevent a whale who already has let's say 1 million BTC (4.7% of the networks value) from committing a holocaust and killing 4 million people to gain another 1 million BTC (another 4.7% of the networks value)? Even if the dead people's bitcoins are lost forever and the circulating supply decreases therfor to 20 million he would now hold 10% of the whole network's value. He could repeat these holocausts until he gains network majority at 8 of 14 million available BTC (and exterminating 28 of 80 million people along the way)

I answered that while this is a possible scenario it's very theoretical but I'm wondering if there is another, better answer maybe from a game theory perspective that incentives good behavior at this endgame stage of Bitcoin?