Nice feature on one of my very favorite Justice League America stories from the Giffen DeMatteis era - Justice League America #38-40 where they battle Despero.
https://www.cbr.com/justice-league-g...-bleak-battle/
Giffen also plotted some very serious and well-done issues of Justice League Europe around the same time. JLE vs The Extremists and Starro were very good. The humor was always present, but it showed that there could be a serious threat along with the jokes.