Tropes

An Arm and a Leg: The imperfect Amazon Omega rips the wings off the Bat Amazon.
Break the Cutie: Mamoru upon seeing both Maehara and Ryusuke die.
Dynamic Entry: Amazon Omega makes his first appearance in his complete form by slamming into an Amazon from a very long jump.
Failed a Spot Check: The team miss the signs that Otaki is turning into an Amazon, simply thinking he has a hangover.
Half the Man He Used to Be: Otaki, after turning into the Dragonfly Amazon and going completely berserk, is killed this way by Omega.
I Cannot Self-Terminate: Otaki tries to get the others to kill him before he completely loses control. Presumably he simply wouldn't be able to inflict enough damage on himself to do it himself.
"I Know You're in There Somewhere" Fight: Subverted, as Maehara trying to reason with Ryusuke/Dragonfly Amazon leads to his death.
I Just Want to Be Normal: Otaki says in an inner monologue that all he wanted to do was be a human.
In a Single Bound: As Amazon Omega, Haruka reaches the site of the battle this way, jumping across entire city blocks at once.
Mercy Kill: Otaki wants his friends to do this to him. When they can't, Amazon Omega ultimately does.
Your Head A-Splode: The imperfect Amazon Omega kills the Bat Amazon by squashing its head so hard it pops with probably the goriest Rider Kick ever.

Recap / Kamen Rider Amazons Ep 2 Beast Inside