[londons_explore]

Yes. An attacker who is prepared to spend the same amount of money as all other network players earn combined can do various attacks.

The goal of the "halve every 4 years, plus transaction fees" model is to make sure the above is never possible for an attacker.

[MattPalmer1086]

I think they just need more than half?

[Repulsion9513]

How can you have more than half without more than everyone else (who by definition have less than half) combined?

[londons_explore]

They either need to sway more than half the miners to their evil side, or they need to exceed the total of everyone else.