•Give sb tit for tat (idiom) -
To give someone something equal to what was given you.（以牙還牙，針鋒相對）
1. They gave me the same kind of difficulty that I gave them. They gave me tit for tat.
2. He punched me, so I punched him. Every time he hit me, I hit him. I just gave him tit for tat.
•Give sb a taste of their own medicine（idiom） -
To do the same bad thing to someone that they have done to you. （以其人之道還治其人之身）
1. I'm glad somebody decided to give them a taste of their own medicine.
2. This team likes to play rough, so let's go out there and give them a taste of their own medicine!
•Spell sth out (phrasal verb) –
To make explicit; to specify in detail.（清楚說明）
1. Be assertive and spell out exactly how you feel.
2. The government has so far refused to spell out its plans.
•Fall prey to sb/sth (idiom) -
To be harmed or affected in a bad way by someone or something. （深受…之害，成為…的犧牲品）
1. Police fear that more senior citizens could fall prey to the thieves.
2. Some of his friends fell prey to drugs.
•Habit is second nature (proverb) -
That which has been turned into a habitual practice will be done with little or no conscious effort.（習慣是第二天性，習慣成自然）
1. Habit is a second nature, so teachers often remind us to make a good habit.
2. Sorry, ever since I worked as an editor I can't help but pick out typos and grammatical mistakes. Habit is second nature!