Would it have to be the coins you personally hold? And do they need to reach an ATH or just something like a 10x?
If you were around in 2013 you may remember coins like Feathercoin, Namecoin and Primecoin. They were in the top 20 coins at the end of 2013 and had big rallies (e.g. namecoin 30x) but didn't reach ATH in 2017.
A lot of big coins from 2017 did not reach ATH in 2021. E.g. XLM, Dash, IOTA, Neo & BCH.
So I expected a lot of the favorites from 2021 to not reach an ATH in 2025 or maybe ever again. I think one of the reasons meme coins did well in 2023-24 was because people lost trust on supposed good projects that no one actually uses.
With that in mind what would you define as an alt season?
For me it's if all coins do a 5x and a few new narratives do outstandingly well.

