That, and Shiro Kazami/Rider V3, while surrounded by fire, using a Rider Punch on his own, horribly mutated sister to fulfill her wish to die rather than live in pain.
Kamen Rider (1971-1973)
The first fight Kamen Rider 1 has with Kumo Otoko and the Shocker foot soldiers. Really got to hand it to the stunt work there, especially for a first episode.
Episode 2's night fights against Komori Otoko and Shocker's combatants.
Episodes 6 and 7. Full stop
To elaborate, these episodes were the first two-parter episodes in Kamen Rider history, and it delves on the MOTW Chameleon searching for the Nazi's hidden treasure in Japan. Of course Hongo found out of Shocker's plot and plans to stop them. Meanwhile, the Great Leader had his scientists find a way to stop Kamen Rider, preventing him to transfrom by confining him to a traphole (where he transformed anyway). The next episode, we're shown Hongo as the Kamen Rider about to be crushed by a descending ceiling, the pressure and lack of wind to activate the Typhoon's turbine resulted in Hongo reverting back to a human form. Fortunately, a Nazi box Hongo acquired from the last episode, in Shocker's hands, was a fake and he told them that only he knows where the real deal was, resulting in Hongo getting out alive and escaping. In the climax, Shocker found the location of the buried treasure and when they opened it... Kamen Rider was inside! Regardless of how Hongo does that, he fought all of the Shocker goons and defeated Chameleon. But after Rider Kicking him, instead of letting him dissolve like the previous MOTW, he Rider Chops him and cracks his skull open! Yeah, the effect was done by smashing a mirror with the Chameleon suit reflected on it, but its implication of how strong the Rider Chop could do against an enemy was quite clear
Episode 13, where Kamen Rider #1 beats up EVERY SINGLE Shocker's Inhumanoids that appeared thus far. There's a reason this episode was adapted into a movie.
While filming for episode 10, Fujioka Hiroshi got into a motorcycle accident - footage prior to the crash was used in the episode. (He apparently remembers up to the point where he took his leg, badly twisted out of position, and realigned it.) This put Rider #1 out of commission, while Rider #2 took over beating the crap out of Shocker. Several months later, Fujioka recovered and returned to the show - and thus the Double Riders were born.
Hayato's debut episode. All of it.
The awesome final showdown between Pirasaurus and Kamen Rider #2 in episode 17. Even to this day the fight choreography holds up pretty well, especially for it's time.