Step 1: Think of validate as the act of establishing that a claim holds up after close checking.
Step 2: Examine fits directly since it means to inspect carefully, and Dig out and Exhume both carry the sense of uncovering something in order to verify it.
Step 3: Disprove works against a claim rather than confirming it, so its meaning is opposite to validate, not similar.
\[\boxed{\text{Disprove}}\]