How to Say "unfounded" in Spanish
The Spanish word for “unfounded” is “temerario” — C1 level.
English → SpanishC1
adjectiveC1formal
referring to a claim or judgment made without proof

Examples
Hacer un juicio temerario sobre su honestidad fue un error.
Making an unfounded judgment about her honesty was a mistake.
La demanda fue rechazada por ser considerada temeraria.
The lawsuit was rejected for being considered baseless.
Formal Contexts
In this specific sense, 'temerario' is almost always paired with 'juicio' (judgment) or 'acusación' (accusation).
Related Translations
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