OPM is as popular as it is, but it always impresses me how far the writing goes to frame Saitama's utterly one-trick-pony schtick, and how well and surprising it's done.
Here, the whole concept of ONE using Suiryu as a complete foil to not only the plot but also Saitama himself just feels great. The character is dragged (sometimes literally) from unassuming to relative omnipotency back down to helpless, from carefree to envious to despairing, all to basically set up Saitama sauntering back in to save the day. All this is done WHILE highlighting the flaws of the minor villains and the heroism of the minor heroes.
I'm no pro critic, but it seemed to me that when Saitama finally saves Snek, that not only gave closure to their first encounter but tied up everything from this arc (or so it seems, with his arrival). Had the biggest smile on my face.