Drowning
Borden is asked to be sure to tie a specific knot for Julia to get out of. Ironically, we don't know what knot he ties, but we do know that she drowns - and the only reasonable deduction is that Borden tied her up in order to kill her.
Grief
After Julia's death we watch Angier go into a mode of revenge, and we don't see much of his grief. Ironically, the final shot shows multiple duplicates of Angier in water tanks that have drowned. It shows us that he was willing to drown himself over and over again every night and it is an ironic way to punish himself for the death of his wife.
Sarah
Sarah has become deeply depressed and eventually kills herself as she doesn't know what man she will get from day to day. Sometimes her husband smothers her with affection and other times he abhors her and she can't handle this and takes her life. Ironically, Borden has caused this because he and his twin brother share an identity, and rather than letting Sarah in on their secret he allows her to go on thinking what she will - even to her own death.
Canary
Cutter shows Jess a magic trick of making a canary disappear and reappear to which she is very pleased. Ironically, Cutter kills one canary in order to make the trick work. He simply keeps that part of the "magic" away from the child.
TESLA
Olivia gives Angier the key word for Borden's diary in order that he can decipher all of his tricks. Ironically, the diary is a decoy to distract Angier from practicing magic. Even more ironical is that it leads to Angier to Nikola Telsa, who invents the machine that duplicates himself.
