甘い: A sweet peach and a lenient judgment
Compare 甘い describing a peach’s sweetness with 甘い describing a father’s judgment about the younger brother. Follow the evaluated target, degree, and tense rather than an assumed ingredient or overall character.
The peach’s sweetness
「この桃はとても甘いです。」 — “This peach is very sweet.” この桃 is what is evaluated, and とても gives the degree of sweetness. 甘い describes this peach’s taste.
Sweetness is different from a report that an ingredient was added. The sentence does not describe adding anything to or processing the peach.
A judgment concerning the younger brother
「弟に対する父の判断は少し甘かった。」 — “My father's judgment of my younger brother was a little lenient.” 父の判断 is the target of 甘かった. 弟に対する identifies whom the judgment concerns, and 少し limits its degree of leniency.
Read a past evaluation of a somewhat lenient judgment. It does not describe a food taste or establish that all the father’s judgments or personal qualities are always the same.
The evaluated target selects the sense
この桃は甘い evaluates fruit taste; 父の判断は甘かった evaluates strictness of judgment. The surrounding target distinguishes sweetness from leniency despite the unchanged adjective.
とても甘い and 少し甘かった differ in degree and tense as well. Keep very versus somewhat and the current state versus the past judgment attached to their respective examples.
What does 甘い evaluate in 「弟に対する父の判断は少し甘かった」?
Show the answer and why
The target is the father’s judgment concerning the younger brother. 少し甘かった evaluates that judgment as a little lenient in the past, without extending the description to all of his judgments or character.