There are 11 words that end with 'niacal'.
| maniacal | ammoniacal |
| demoniacal | simoniacal |
| egomaniacal | monomaniacal |
| pyromaniacal | dipsomaniacal |
| bibliomaniacal | megalomaniacal |
| nymphomaniacal | |
Note: These 11 words that end with 'niacal' are found from the USA & Canada version of the tournament Scrabble word list.