The latest PK2 engine, also known as Greta Engine, made by Saturnin and forked from PK2 SDL by Danilo.
Saturnin also shared the Greta Engine Source Code for Linux and Mac.

✔ PROS ✔

• It is the most recommended Engine, as it's very updated and fixes lots of bugs.

• It is constantly receiving updates, unlike the other engines.

• It has a lot of new features such as Lua Scripting, new sprite features, new level features, and more!

• Most old content should be compatible and work correctly in Greta Engine, except Community Edition episodes.

• There is a possibility (not confirmed), that this engine will be available on Steam in the future.

❌CONS❌

• It lacks some legacy exploits and bugs which were used to speedrun Rooster Islands, such as the ice cube exploit.
  
  

Also known as PK2 SDL.
It was the first PK2 version to run well on modern computers and allow Android ports, made by Danilo.
There is also an Online Version of PK2 SDL.

✔ PROS ✔

• It adds a lot of cool features and improves some things compared to Legacy PK2.

• It adds support to .zip episodes, removing the annoying necessity to extract episodes every time.

• It is compatible with most level and sprite editors created before Greta Engine.

❌CONS❌

• Its creator became inactive, so this version is discontinued and won't get more updates.

• Version 1.4.3 seems to be the most stable one. Higher versions have serious bugs, so they're not recommended.

• It contains memory leaks which crash the game and will probably never be fixed.
  
  

A PK2 version that had cool features, but it was discontinued. Made by Daeta.

✔ PROS ✔

• It added interesting features such as checkpoints, custom switch timers and secret levels.

• It is compatible with most level and sprite editors created before Greta Engine.

❌CONS❌

• It got discontinued.

• It was buggy and physics were reported to be different from the Legacy PK2.

• Community Edition episodes won't be compatible with other engines.
  
  

The official, legacy Pekka Kana 2 version from 2003, by Janne Kivilahti and Pistegamez. Sadly abandoned.

✔ PROS ✔

• It is purely official.

• Some people want to play this version mainly due to nostalgia. It has a different feel to other Engines.

• The majority of old episodes were designed for this version, so they should work fine here.

❌CONS❌

• It got discontinued.

• It's super outdated and barely playable. You need tools like Dxwnd to be able to run it.

• Custom Episodes were supposed to be extracted, which could lead to issues with overlapping sprites.

• Nowadays, almost nobody uses this version to create episodes, so new episodes most likely won't work here.
  
  

A PK2 tool by Daeta that lets you view and modify some aspects regarding PK2's indexed 256 color palette.

✔ PROS ✔

• It could be super useful for people who can't get other programs to view/edit palettes, such as Gimp or Aseprite.

❌CONS❌

• It is underrated. Not many people use it so it wasn't tested much.