Finding x,y coordinates where y is largest

MaximalBy[A, Last]

{{-3, 0.523614}}


A[[Ordering[A[[All, -1]], -1]]]

{{-3, 0.523614}}

Note: Ordering typically is faster than alternatives for large lists.

SeedRandom[1]
a = RandomReal[1, {100000, 2}];
r1 = a[[Ordering[a[[All, -1]], -1]]]; // RepeatedTiming // First

0.0017

r2 = First[SortBy[a, -Last@#&]];// RepeatedTiming// First

0.017

r3 = TakeLargestBy[a, Last,1]; // RepeatedTiming // First

0.039

r4 = MaximalBy[a, Last]; // RepeatedTiming // First

0.065

r5 = First[Sort[a, #1[[2]] > #2[[2]] &]];// RepeatedTiming// First

1.88

r1 == {r2} == r3 == r4 =={r5}

True


First[Sort[A, #1[[2]] > #2[[2]] &]]

{-3, 0.523614}