The worst bulbs I've personally seen for flicker were dimmable ones.
The non-dimmable variant from the same range had no noticable flicker.
Price paid also seems to be no indicator of quality – I've had premium LED bulbs from major makes, bought from a reputable wholesaler, that have died after 6 months within days of each other.
I've had cheap no-name imports that have lasted years and had no flicker.
However, there are also LEDs that support legacy dimming, but again translate less current into different flicker patterns...
In other places I don't have dimmers but have low-voltage (12V) cans. Lots of flicker issues there too, presumably due to the 120->12V transformer at the can.
And then I have a light fixture that's both dimmed and a custom 12V setup. I've given up on finding a working dimmer/LED bulb (MR16 GU5.3) there. Probably need new 12V transformers?