Destroyed the Rachni. No dialogue with Asari. Actual effect on ME2 this has? None.
Killed the Council. No longer able to be a Spectre. Actual effect on ME2 this has? None.
No matter what choices you made in ME1, the best ending in ME2 is possible. Making all renegade or all paragon choices in ME1 doesn't affect how difficult it is to get the best ending. There is no negative impact for renegade choices, and no positive impact for paragon choices.
Paragons get a few more dialogues because they saved more people, but these don't impact anything. They provide no benefit and no bonus.
Actually you can become a spectre again if you let the council die. Atleast with Anderson as councilor. But that is beside the point. Even if it does not effect you're gameplay as such, with a dead council:
- humanity is distrusted by the other races
- the citadel fleet is slow in rebuilding
- The new council is busy with itsself instead of the galaxy
Seems to me like a bad start point for ME3 compared to were you are if you safe em. Sad thing is my main char didn't even kill them on purpose to be bad ass. I was just scared that when the citadel opened there wouldn't be enough ships to take sovereign down in time. Was perhaps a tad bit too convinced by the story that I could fail

.
It would be neat if some risks you take as paragon would backfire aswell though. Like blowing up the collector base, but more then just that one. But not the Rachni! The Rachni are my sweet pets that I am gonna feed reapers

P.S. The asari mercenary ended up dying even on my paragon chars. She reached for her bloody gun after claiming she was innocent! I shot her in reflex with the renegade intervention.