These might be Pixel only features, but the few that always get iPhone users envious of my phone are:

Battery sharing - Turning the phone into a wireless charger for other phones, including iPhones.

Now Playing - Display whatever music is playing on the lock screen, and keep a history. Great when you're at a bar and don't want to open up Shazam or want to go back and see all the music your friend was playing in the car.

Ad Guard - Block ads, even in apps.

If you use the 3 button navigation, there are options for long press of buttons. "Kill foreground app" as back button long-press action is just indispensable when something goes wrong.

In developers options, turning the animation speeds to .5x

Don't know if that's really an underrated feature, but would like to mention it anyway. Everything feels much faster after that. Pretty much the first thing i do when i have a new phone.

NewPipe, ReVanced patches, screen rotate with the popup, KineStop, and if you’re adventurous: dual boot different ROMs using A/B.

Android has support for keyboards. Both USB and Bluetooth keyboards work well and can be used for longer typing.

Pin a app to the screen, so if you need to let someone use their phone they can't get super nosy.

owner account can have a work profile, separate apps, have two versions of the same app, or just put some apps behind another fingerprint/password (can be different then the main phone unlocks)

Multiple user accounts (totally different accounts, totally different apps) : great if you want to let a kid play games, or let someone search the internet, or if you want to be really clean and keep work apps totally different. Mostly useful on tablets to let multiple people share the tablet.

The ability to run open source apps from fdroid, newpipe is an amazing game changer for anyone who watches youtube. (no ads)

Not sure if this counts as "underrated" but Quick Share / Nearby Share. Its just Airdrop but for Android, not much to explain. It's built in to all modern Android versions, and some older devices might also have it if they are new enough to have the "Google Play System Update" option on their phone as a separate update option from the main OS update.

Edit: Actually, its reportedly available for every android phone with Android Version 6.0 or newer.

Try other app stores like fdroid

On the calendar, I can set people's birthdays with a yearly reminder so they think I'm super thoughtful for remembering their birthdays. But the phone notified me.

Other ROMs like Lineage.

An application like tasker makes you realise the weird and amazing stuff you can do.

Check out the eye gaze function. Also Action Blocks. They're both cool assistive tech things that can be helpful, but trying them out shows you how difficult and exhausting it would be to have to use them for every task.

Some Android versions let you map the flashlight to the volume buttons and you can toggle it by pressing both at the same time. The option can be found in the system settings. If your OS does not have the setting, you can map the keys with an app like Torchie. It's probably the feature I use the most on my phone, I couldn't live without it at this point.