What would be the eqivalent and informal way to say colloquially" He was a nice guy" Like for a dearly departed etc.

...you might say:

Fear cneasta a bhí ann.

...or just

Fear deas a bhí ann.


...or if you wish:

Ba chneasta an fear é. / Ba d(h)eas an fear é.

_________________
Bí cinnte de go nglacfaidh triúr le gach aistriúchán a thabharfar.
Be sure to get three in agreement with a translation given.