Michael Read says

Maybe, in a decade or two we may find a word more descriptive than apesh!t but, right now, it fills a niche perfectly.

There's always "bugf*ck nuts."

crassfool

Agreed yet the modifier to ‘nuts’ makes ‘bugf*ck nuts’ a compound relying on the modifier’s emphasis on ‘nuts’ to give impetus to ‘nuts’ that ‘apesh!t can do as a single word. Also, raised as a query delineating either, is bugf*ck nuts an equivalent of apesh!t or is one more limiting to observance of a turn of phrase? Fowlers is of absolutely no help on this. It could also be a regional descriptive.

I would also include ‘wrangy’ in this but is it a lesser to bugf*ck nuts and apesh!t. To go wrangy is being off center while bugf*ck nuts and apesh!t mean further than off center. The argument is then is bugf*ck nuts more away from the mark that apesh!t. I would argue going apesh!t is farther out that bugf*ck nuts.

Once a descriptive was, “He has lost all reason,’ and that covered it. We could say, “He went bonkers,” and that that understood. However, times have changed and going apesh!t is a descriptiveness I feel is above that of ‘bugf*ck nuts.

Yours in explaining modern verbiage,

MichaelR