Support the Korath, ally with same, then cackle gleefully while they spore the shit out of everyone and you buy the newly invaded 0 pop planets for pocket change.

Buying newly colonized low pop planets for nothing but influence.

Buying everyone's asteroid miners with influence to use them as free scouts.

Paying one civ to attack another as soon as you meet them, interrrupting both civs' colony rush.

Well, I might have given someone Industrial Sectors or something else expensive to build right before a war with them 'happened.' The AIs don't seem to know how to say no to untimely upgrades.

Research all the Influence techs early, along with the Diplomacy techs. Buy all their BC in exchange for influence so they don't have money to rush buy things with. Having no cash the AI will build attackless and defenseless hulls in hopes of upgrading later. Just before declaring war, buy off all their ships you can weither they have weapons or not, and upgrade those that don't. -Perferably using influence instead of cash. Then declare war and laugh as the AI doesn't have any ships to defend against the invasion.

If you want to be really evil, sell/give the AI a higher-level tech in production, moral, and/or research so all their planets will be concentrated on social production. You're almost assured of no retaliation as you send in the transports to take over.

Pay the Dregin to go to war with tech or ships, let their SA go off, creating more ships for them to maintain...rinse/repeat until their economy is tanked.  Combine with sabotaging their econ buildings to further bottleneck their economy, since now theyare also spending on spies....Want to see a superpower go broke and collapse upon itself?

Just out of curiosity, what is the highest difficulty level you have played so far?

Tough. I go for broke and call their bluffs on cash figures rather than odds against.

This way, my brain can still evaluate instead of suffering from weird Mega conditionned Events.

Poker? Naaaa, too easy. Although i tried managing Black-Jack & Roulette tables in pre-training fast track for the Casino of Montreal in summer 93 -- but, as it happens, turnover was much lower than they first anticipated to get a formal job offer. Life went on... still, i never could wrap my mind around Bond's straight flush of spades in Royale -- i at least had the satisfaction of witnessing four Aces delt in a single round, mine being uninsurable.

Break even or keep losing - for tokens. Now, that's suicidal.