I've used VLC Media Player so far - is there anything "better"? Is there any good portable player?

I've been using Windows media player classic for many years. It never failed me. It plays anything I want and never crashed on me.

In Windows, I like PotPlayer more than VLC.

I don't use it because I feel more comfortable with open source media players, but I agree that PotPlayer is a nicer than VLC.

MPC-HC and/or MPC-BE. I'm using both. Usually the zip or 7z downloads are portable versions.

In general I agree, but I make exceptions for some good freeware such as PotPlayer, foobar2000 and IrfanView.

Another vote for MPC-HC, although I use VLC too. Both have their advantages.

There's also mpv (https://mpv.io), which is relatively new but rather praised by people who tried it (I personally still use VLC for most things, but MPV did prove better for me at one aspect - a certain DVD that stuttered near the end in VLC played just fine in mpv). The installation page links to a site with windows builds of the stable releases and they are 7z files with the executable and other necessary parts (e.g dlls) contained inside, so it probably fits your criteria as a portable player.

it depends. If you are looking for playback of everything without extra stuff installed/all-in-one installer, VLC is the way to go. If you wanna install a codec pack, MPC:HC or MPC:BE are the way to go. If you wanna watch 4k HDR content on a non HDR display and can output 10-bit HEVC, download the player from mpv.io (it has very little to no GUI but it displays the HDR content like it was from a regular blu-ray) which has the bonus of being multiplatform.

Antivote for MPC-HC and variants; the HC project was discontinued due to a lack of active developers and was last updated sometime last year.

But I will suggest MPV as an upcoming hopeful.

Otherwise, VLC is still champion.

MPC-HC was discontinued? Oh my...

I'd still suggest it anyway. It's been pretty decent, far more so than VLC with me.

https://forum.doom9.org/showthread.php?t=175209

MPC-HC is still being maintained.

At this moment (after system reinstallation) I'm using it and it lacks a few things for me - like keyboard shortcuts are not really configurable and I can not find the way to add external subtitles without installing additional software (and if I need additional software for them then why not going back to VLC). Yes, I've heard about it and this is one example of the reasons why I still have not reinstalled VLC yet.
I'd like to read more opinions about it.

Same situation here. But recently author of one Firefox extension I've used pointed me in direction of mpv.
https://addons.mozilla.org/en-US/firefox/addon/yt2p/

And as I'm after system reinstalation then it's good time to ask such questions if mpv (or any other player) is maybe currently better (before I install VLC again).