ならまだしも

JLPT Level: N1
Meanings

If it were X, that might be acceptable, but Y is not acceptable

A is tolerable; B is not

It's different when A, but not when B

It's not so bad when A, but B is worse

Usage

Noun + ならまだしも

Plain form verb/adj + ならまだしも

Na-adjective + ならまだしも

exception clauses using 〜は/〜でも + ならまだしも

Explanation
This expression is used to compare two situations: a relatively acceptable or minor case versus a much less acceptable or more problematic case. The first part (before ならまだしも) is something that could be tolerable or understandable; the second part (after ならまだしも) is worse and thus not acceptable or believable."
子供ならまだしも、大人がそんな嘘をつくとは信じられない。
こどもならまだしも、おとながそんなうそをつくとはしんじられない。

If it were a child, maybe, but an adult telling such a lie is unbelievable.

百円ならまだしも、千万円の借金はきつすぎる。
ひゃくえんならまだしも、せんまんえんのしゃっきんはきつすぎる。

If it were 100 yen, that would be fine, but a debt of ten million yen is too harsh.

私が自分でやるならまだしも、他の人に任せるなんて無責任だ。
わたしがじぶんでやるならまだしも、ほかのひとにまかせるなんてむせきにんだ。

If I could do it myself, that would be one thing, but leaving it to someone else is irresponsible.

遅刻するのは仕方ない。ならまだしも、連絡もなしに来ないとはひどい。
ちこくするのはしかたない。ならまだしも、れんらくもなしにこないとはひどい。

Being late is understandable. But arriving without any notice is terrible.