The opposite of 我爱你. (Wǒ ài nǐ. I love you.) is 我恨你. ( Wǒ hèn nǐ. I hate you.)
恨 (hèn) is to hate or to regret. This word can also serve as a noun, meaning hatred. As with love, there are various flavors of hatred and resentment. 怨 (yuàn) as a verb means to blame or to complain. As a noun, it means resentment or antagonism. And 怨恨 (yuànhèn) means to hold a grudge against someone, or the resentment or grudge itself. 仇恨 (chóuhèn) is hatred between enemies. A deep-seated bitter hatred is called 深仇大恨 (shēnchóudàhèn).
恼恨 (nǎohèn) is to hate and feel bothered. 痛恨 (tònghèn) is to utterly hate someone or something. 憎恨 (zēnghèn) means to detest. 嫉妒 (jídù) is to be jealous of someone. Therefore, 嫉恨 (jíhèn) is to hate out of envy. 愤恨 (fènhèn) is to hate with indignation. These words can also be used as nouns, as the following example shows:
Tā de yǎnshén lùchū wúxiàn zēnghèn.
The expression in his eyes revealed immeasurable detestation.
In the above sentence, 无限 means without limit, or infinite.
怀恨 (huáihèn), or 记恨 (jíhèn), means to nurse a hatred or resentment.
Tā duì nǐ huáihèn zài xīn.
He bears deep grudges towards you.
可恨 (kěhèn) is an adjective that means abominable.
Nà xiǎotōu zhēn kěhèn.
That thief is really despictable.
The phrase 恨不得 (hènbude) expresses a great desire to achieve an unlikely result or effect and the regret of not being able to do so.
Wǒ hènbude mǎshàng fēi dào nǐ shēnbiān.
I wish I could fly over right away to be by your side.
后悔 (hǒuhuǐ) means to regret or to feel remorseful. Therefore, 悔恨 (huǐhèn) means to be deeply remorseful. Here, the “resentment” is towards oneself.
Wǒ hǒuhuǐ méiyǒu dǎdiànhuà gěi tā.
I regret not having called him.
Duìyú nà shìjiàn, wǒ gǎndào fēicháng huǐhèn.
I feel extremely sorry about that incident.
Please note that when by “hating” you mean “being displeased”, you should use 不高兴 (bù gāoxìng) rather than 恨 (hèn).
Wǒ bù gāoxìng tā yòu chídào le.
I hate that he’s late again.
What else will irk you?