Just lost my 5 hour game as Advent. I spent alot of time and resources on trying to gain favor with a faction. On my relationship and diplomacy screen, it says "warming". On his tab in relationship, he hates me. I only figured this out and was really p***ed off since I did most of his missions, gave resources and sent envoys. Eventually my neighbors ganged up on me and the other faction I was trying to be friendly with.
If you can manage to get a cease-fire (get relationship research upgrades, donate credits and stuff, do missions if you have to), and don't piss them off more, then you can send an envoy cruiser to each of his planets, which'll probably keep him from breaking the cease-fire, eventually leading to peace treaties (envoy cruisers increase foreign empires' opinion of you when the envoy is in the foreign-owned gravity well). After that, it's virtually guaranteed that you'll remain at peace (until you decide to break the treaty).
This is exploitable, though, since (if you don't care for the Pacts) you can then build starbases at their worlds, break the peace treaty, and quickly gain control of his entire territory.
Any advice on this would be great.
On single-player, it's easy. Build a starbase as quickly as possible at all choke points, upgrade them as needed, and fill out every spare logistics slot with trade ports. Any potential attacking AI fleet will suicide themselves on your starbases: you'll be free to research and fortify and save to your heart's content until you feel like building an offensive fleet.
Secondly (this is a minor problem), sometimes my bombers will stop attacking the target I give them and will attack something else. Im sure this didnt happen eariler in the game. I lost a cap trying to take out structures for missions, and the building was almost destoryed till the bombers decided to take on something else.
This is due to a Vasari quirk. Is it a bug, or by design that bombers stop attacking structures at that point? It's pretty stupid for them to stop attacking when incoming damage is only reduced by a slight fraction: it could mean 30 second's worth of firing wasted, unless the player catches on.
I lost a cap trying to take out structures for missions
The AI doesn't give out missions very intelligently...
How can you break an alliance between two AI factions?
Start by killing their envoy cruisers at their respective worlds. That should go a long way towards lowering their relationship towards each other.