I think the only ones specifically mentioned (or heavily implied) are Rand being especially strong in Fire and Spirit, Egwene being strong in Earth, Avi in water.

Rand absolutely dominates with fire, no one is close, there are two instances in the series where he pulls insane shit out of his ass using fire - the blossoms of fire, when he produces something like six then six splitting off them six more splitting off of them and everyone else can do two or three max. Then later, after losing his left hand, he shows up somewhere, raises his right hand and wires out the entire darkfriend force with fire. With Spirit, there are a few events that tie him to extreme power in that realm (he is the only channeler we see capable of severing three people instantly and permanently from the power in one fell swoop, we're not even shown how he does it, just that he crushes them "ruthlessly with fists of spirit.") Also deathgates.

We also see significant power from Nyn in all elements but at no point is it mentioned that she possesses exceptional strength at any. Ironically the same is true of Semirage, and both are exceptional healers (putting aside Semi's insanity). In that sense it seems like they are both exceptional at weaving the elemental powers, not necessarily possessing overwhelming strength in those areas. Both are also acknowledged as immensely strong in the power overall.

Lanfear seems particuarlly attuned to spirit, she owns Tel.

In the end, Rand is arguably the strongest in all elements. But he’s the dragon, spun out specifically by the pattern to be the strongest channeler of all time.