Master of Orion/Killing the Guardian

Something to note here that is completely unlike in Master of Orion 2 is that there is only one enemy in space that spawns guarding a planet. Master of Orion 2 has upwards of 10 on a given map and they expect these to be beaten fairly early in order to gain access to better planets in the mid-game.

In Master of Orion 1, the Guardian is the only thing guarding anything.

Also, it is very very difficult to kill early. It is a very strong ship and will tear apart most fleets that are not designed specifically to beat it. Even if ships are designed specifically to beat it they often have a really hard time doing so because the ship is just that strong.

Another thing to note, it isn't really that important to beat the Guardian if you want to win most of the time. The only time it is often required is if you are in a losing position in the very late game and you can't research tech fast enough to dig out of the hole.

Usually, beating the Guardian is just a status symbol more than anything else.

Sirian posts lots of walkthroughs of games he has played on the Impossible difficulty setting and not a single one included defeating the Guardian as shown by his omitting it completely from his play by play analyses.

Other pros often experience the same thing.

One other thing, Orion counts as a sort of Ultra Artifacts planet. Every time you beat the Guardian, you get the Death Ray, a weapon with a maximum of 500 damage per shot) AND you get 5 free random techs. Usually those are high level techs as well.  Random generated techs from Artifacts planets get you techs that are up to 10 levels higher than what you already have.  When you get to the stage where you can seriously think about beating the Guardian, you might be level 40 in some fields.  That means you could jump right to the highest tech in a field if you are lucky.  This can also get you techs that were not available in your tech tree.  This is a huge technological boon.

If you think you can beat the Guardian and you are behind some other races, it could help you catch up technologically.