At first Pachis attended painting lessons at the Accademia di San Luca and later at the Accademia di Belle Arti di Napoli.
He was still very young when he was working as a servant for a wealthy Englishman, who saw his work and offered to pay his expenses to study in Italy. Pachis was influenced by the work of Dionysios Tsokos and the philhellenes artists of the 19th century. After an educational journey to various European cities, he returned to Corfu in 1870, where he taught briefly at the "Kapodistrias School".
After that, he established his own private art school.
Periklis Tsirigotis, Angelos Giallinas and Georgios Samartzis were among his best-known students. His most famous historical scenes are depictions of the assassination of Kapodistrias, the Dance of Zalongo and the hanging of Gregory V. He also painted portraits, landscapes and illustrations for hagiographic works.
He is considered as one of the first painters of the Heptanese School who created landscapes and genre scenes. Pachis" artistic creation also includes the iconography of the Orthodox Greek Church of Durrëson
His major showings include the National Exhibitions at the Zappeion in 1875 and 1888, and the Exposition Universelle (1878).