Be careful on loyalty in Mass Effect 2.
If you want to make sure every character survives the final battle in the game, you will need full loyalty from everyone which is hard to get.
Get to 80%
Before you do Jacks loyalty quest, you should get up to 80% paragon or renegade points. Otherwise, she fights with Miranda and you have to choose a side and get to 100% to woo them back. The same holds true for doing Legions side quest with him and Tali. If every person is not loyal after you enter the Omega 3 relay, you will not survive. Also, upgrade your ship fully. My advice, is just go with all paragon or all renegade responses to everything as they really don't effect the turnout of the game, and get to your percentage fast. I spent 5 extra hours grinding paragon points to get Miranda back.