CREATE TABLE table_204_621 (id DECIMAL, "no." DECIMAL, "date" TEXT, "tournament" TEXT, "winning score" TEXT, "margin\ of victory" TEXT, "runner ( s ) -up" TEXT)

in which tournament did he have the biggest margin of victory ?
SELECT "tournament" FROM table_204_621 ORDER BY "margin\nof victory" DESC LIMIT 1
SELECT "tournament" FROM "table_204_621" ORDER BY "margin\nof victory" DESC NULLS LAST LIMIT 1