John Gill Commentary 2 Kings 15:27

"In the two and fiftieth year of Azariah king of Judah Pekah the son of Remaliah began to reign over Israel in Samaria, [and reigned] twenty years." — 2 Kings 15:27 (ASV)

In the fifty second year of Azariah king of Judah Pekah
the son of Remaliah began to reign over Israel in Samaria
Which was the last year of the reign of Azariah:

and reigned twenty years ;
which was a long reign for an usurper and murderer.