Step 1: Revaluation at admission.
When a new partner is admitted, all assets and liabilities may be revalued. But one asset that is always adjusted is Goodwill.
Step 2: Reason.
Goodwill ensures that existing partners are compensated for the reputation and profits earned by the firm before the admission of the new partner.
Step 3: Conclude.
Thus, at admission, Goodwill is compulsorily revalued/adjusted.
Final Answer:
\[
\boxed{\text{Goodwill}}
\]