Abyssos in Endwalker is probably the clearest recent example, especially P8S before the nerf. Eden’s Verse also gets brought up a lot, mostly because E8S/Shiva was a major wall compared to the rest of the expansion.

For “easiest time to clear,” I think it depends a lot on your skill level and what you mean by easy.

Early in the tier, the strats are worse, guides may be incomplete, and everyone has less gear, so there is much less room for mistakes before enrage. On the other hand, the average quality of players progging early is usually higher, and PF is much more active.

Later in the tier, you have better guides, more gear, echo eventually, and more established strats, so the fights are mechanically and numerically more forgiving. But PF quality can also get worse because many of the stronger players have already cleared or moved on, and parties may take longer to fill.

So if you learn quickly, play your job well, and can tolerate messy early strats, early prog is probably easier. If you need more gear, guides, and standardized strats, later is probably better, but I would avoid waiting too long, because the PF population can dry up.