I originally started writing this as a post for another thread, but after finishing it I thought I would post it as a new post.
Hopefully this will be of some use.
Some background on my experience...
I have won many Gigantic games on Suicidal.
In a few of those games I personally researched/or stole every single tech. I didn't trade for any techs.
I don't do sneak attacks or wars that start and end in one turn (it simply isn't necessary).
Winning on Suicidal takes time because mico-management is what it takes. Every single turn I go to each and every planet and set the sliders depending on what is going on.
I have won with several different strategies, trying to see what works and what doesn't work.
The key is always micro-management.
In my current game of Dark Avatar I won the game (I still have to finish, but I can already tell I won) by ignoring most of the colony rush.
I stopped the colony rush phase at least 1 year before the AI stopped. While the AI was pumping out colony ships I had less than 10 planets producing ships and had my military slider set to 1% with those 10 planets focusing. I wasn't building war ships or colony ships. I had 8 trade routes up and running at least 1 year before any one of the 9 other nations had even 1 trade route established. I had an economic resource and a moral resource fully build as soon as possible.
I have fully developed planets. I put my social slider at 49% and my research slider at 50% and I developed my relatively small empire.
Anyway on to the point of my post....
Here is my list of the 10 stupidest things that the AI does in order of when they start making the mistakes.
1) They don't build explorer ships to find anomalies.
This doesn't need any explanation. Explorer ships can find anomalies, locate exceptional planets, and locate glactic resources (upgrade the explorer to a constructor).
2) They don't research engiine technology soon enough.
My slowest ships are ususally moving at 6 while the AI is building ships that move at 1 or 2. When I start war my ships are twice as fast as their ships. I would NEVER build a ship without an engine. What a waste of BC.
3) They don't build enough factories on their planets.
The smaller the planet the dumber the AI uses the planet. I am often invading planets with NO factories. The AI has NO idea what it is doing. The AI should completely fill a planet with low end factories BEFORE it starts building some massive building that will take 1 year or more to finish. Duh. Just because a planet is small does NOT change the fact that you will need at least 4 or 5 factories to get a planet full functional. The AI sometimes builds power plants BEFORE it builds factories. Dumb. Dumb. Dumb.
4) The AI continues the colonization period way, way, way, way too long.
Seriously, there are dozens and dozens of unused colony ships all over the place. I would NEVER send a colony ship to the other side of the map. What would be the point? When I get there the planet will have been claimed or if I do get a planet it will just get flipped or invaded if I can't get at least a few planets together in a group. I recently destroyed an enemy colony ship that was upgrading to something else. It was going to take over 100 turns. Duh. It spent money doing this?
5) The AI will send out colony ships with less than 200 people in them.
Colonizing planets with these small populations is just a waste of time. These planets flip instantly and even if they don't flip they take forever to develop into income producers. I have seen some with as few as 25 people.
(Combine point #5 with point #3 and they are just taking up space)
6) The AI does NOT understand the importance of unique buildings.
As far as I can tell the AI never makes any real effort to either make these buildings or to finish them.
Finishing these buildings is one of my main objectives early on. In my current game of DA I have managed to build every single unique building first. The Korx didn't even bother to start the Galactic Bizaar.
7) The AI doesn't specialize planets.
This is even more important in DL with the power planets and the research specializers. The AI builds too many starports and generalizes too much.
8) The AI doesn't seem to realize when a building is completely pointless.
The AI builds planitary defence buildings. The very first thing I do when I invade their planets is upgrading these worthless buildings into something useful...
Worthless buildings: Orbital Fleet Manager, Hyperion Fleet Manager, Secret Police Center...
9) The AI tries to defend each planet rather than defending each sector.
The AI defends each planet as if they are isolated from each other. If there are 5 planets in a sector it will have 1 ship on each planet with 1 or 2 speed. My small fleet can easily destroy them one at a time. If they had engines and left orbit they could be in a fleet which could then actually defend the sector.
A planet deep in their territory does NOT need a defender. 99% of my planets are undefended. I defend by having mobile fleets on the border of my empire.
10) The AI doesn't understand sacrifice, or long term planning.
For instance the most aggressive and militaristic nations don't seem to understand that the quickest way to military dominance isn't through military reasearch but through social build up. The most war interested AI races won't sacrifice early military dominance for a true military dominance.
What good is having the best weapons and largest ships if you don't have the social infastructure to build these ships?
You can also see this with regards to what buildings it will build. In DL the AI doesn't even bother to build old tech once it gets new tech.
You can actually destroy an enemy simply by giving them high-end tech. Give them the tech for the biggest factories and that alone with prevent them from competing. This should have changed with DL but I still see tons of enemy planets where they start by building the highest most expensive factory, or they will start by building the most expensive power planet.