Czechia: IMO pretty durable

• Two chambers – House and Senate
• Each has a diferent election system => different composition
• Upper house has staggered terms, takes 6 years to replace
• Need 60% in both for constitutional changes

Here comes the clever part:

Abolishing democracy would requite breaking a Catch-22. All you need to govern is a majority in the lower house. Hence populist leaders only fight to gain majorities in the House. The Senate is powerless when it comes to everyday policy (it can be overruled) and only has teeth when it comes to blocking changes to the constitution. Most populist voters find the Senate pointless and hence do not go to vote in its elections. The only people who go to vote in Senate elections are those who understand its importance as a constitutional break. So the chamber self-filters an electorate that finds democracy important.