‘The angriest man I have ever seen’ - The full version in Irish, using the structure above: An fear is mó a/go raibh fearg air dá bhfaca mé riamh. With the two relative clauses it seems a wee bit clumsy to me (but maybe not in the least to a native or anyone else), so maybe: An fear is mó/ba mhó fearg dá bhfaca mé riamh (or of course a chonaic mé).

An t-é is mór caint ní h-é is maith ciall go minic. Often the person who is great of speech is not the person who is good in sense.
Is minic nách é an t-é is uasal cáil is uasal méinn. It often happens that it is not the person who enjoys the noble name that has the noble dis- position.
The is which grammarians set down as the SIGN of the superlative, is in reality nothing but this relative is. An fear is mór caint is exactly the same construction as an fear is mó caint.
An fear is mór caint. The person who has much talk.
An fear is mó caint. The person who has more talk (than anyone else), i.e., the man who has most talk.
An fear is feár. The man who is better (than any one else), i.e., the man who is best.
An fear is óige. The man who is younger (than any one else), i.e., the man who is youngest.
An fear is sine. The man who is older (than any one else), i.e., oldest.
An fear ba threise. The man who was stronger (than any one else), i.e., the man who was strongest.
<L 20> An fear dob óige. The man who was younger (than any one else), i.e., the man who was the youngest.
An fear dob fheár. The man who was better (than any one else), i.e., the man who was best.
An fear ba mhó caint. The person who had more talk (than any one else), i.e., the man who had most talk.
An fear ba mhór caint. The man who was of much talk, i.e., the man who had a lot of talk.
Ba mhinic nár bh'é an fear dob uasal cáil an fear dob uasal méinn. It frequently happened that it was not the person who had the high name that had the noble dis- position

Hang on - is “ní fhaca” actually “ní fheaca” in Munster Irish? I.e [ni: akə], not [ni: ɑkə]???