Assuming the table prefix is wp_, and if the installation is not multisite, then the following query would show you the user ids, coins and balances that are negative:
SELECT
account,
symbol,
SUM( IF( amount > 0, amount - fee, amount ) ) AS balance
FROM
wp_wallets_txs
WHERE
status = 'done'
GROUP BY
account,
symbol
HAVING
balance < 0;If you are on a multisite installation with multiple blogs, you should also group by blog_id:
SELECT
blog_id,
account,
symbol,
SUM( IF( amount > 0, amount - fee, amount ) ) AS balance
FROM
wp_wallets_txs
WHERE
status = 'done'
GROUP BY
blog_id,
account,
symbol
HAVING
balance < 0;