A great second half to the return of the Fatal Five in Adventure 366 (March 1968), though at no point do Superboy and Validus face off in a boxing ring, despite the cover.
While Cosmic Boy, Superboy, Brainiac 5, Shadow Lass and Karate Kid manage to avoid the Talokian army until the find and destroy the machine controlling their minds, the Fatal Five run rampant on Earth, capturing Metropolis.
The Five discover that the key they need to unlock the U.P. weapons cache is in the Legion Clubhouse, but when they get there, the five Legionnaires are already there, having returned from Talok VIII
I suppose I should have said four Legionnaires, as Shadow Lass is not a member at this point. Brainiac 5 wonders why she has chosen to accompany them, and we discover that Shadow Lass has fallen for him. And its enough of a crush that she is willing to abandon her home and put herself in deadly danger for it. Still, Brainiac 5 dismisses this possibility as “illogical.” He likes using this word a lot in stories from this time, probably because Spock uses it on Star Trek, which was on television at this point.
Besieged by the Fatal Five, Shadow Lass asks to join the team, making her the first member sworn in in the midst of battle.
And she proves herself quite a capable member, taking out the Emerald Empress despite her broken arm.
The 5 teammates battle the Fatal Five to a draw, but when the U.P. army arrives the Fatal Five flee.
The Fatal Five return again a few months down the road.