You can find league tables in Bloomberg (available in the Business Library).
Type MA and press the green GO key. On the resulting page, use the M&A League Tables Search.
For Underwriter Rankings for debt, equity or syndicated loans, enter LEAG or LTOP. For Legal Advisor rankings, enter LALT.
Capital IQ (available in the Business Library), screening tool allows you to create league tables. Select Screening > Transactions and choose specific criteria.