Worst opening for white?


Of the three options you've provided, "h3" (the move 1. h3) is often considered the least popular and least aggressive. While it doesn't necessarily lead to an immediate disadvantage for White, it doesn't control the center of the board (which is a common opening principle) and doesn't contribute to the development of White's pieces.
Moves like 1. e3 and 1. a3 are less common but not necessarily "bad" opening moves. They can be used as part of a flexible opening strategy, where White aims to develop their pieces later based on Black's responses. However, these moves also don't directly influence the center and can potentially lead to passive positions if not followed up correctly.

1.h3 Clemmenz Defense 45:51@1m =
1.h4 Desprez Opening 45:51@1.6m -0.5
1.f3 Barnes Opening 46:51@2.9m -0.6
the clemmenz has the worst performance stats by a very tiny margin
the grob actually has slightly WINNING stats at 50:47@6.5m -1.5, you can't trust stalefish's evaluations to pan out in the real world where often its choice is the worst performing option of many. I have bad stats against the grob myself. it's tricky, unless you're playing WORSTfish
According to most engines, and myself, it’s 1. g4, as it has all of the same problems as 1. f3 plus you’re likely to lose a pawn and screw up your structure even more.