I could kill you! I swear I could!

我要杀了你！我发誓我要。

《柯林斯英汉双解大词典》

"From now on," said the man, horrified,"I swear I shall never again taste fish."

“从现在起，”那人吓坏了，他说，“我发誓再也不吃鱼了。”

youdao

I could swear I remembered seeing rabbits in the snow a couple of times, I means hares, that were brown.

但是我能发誓我记得有几次在雪地里看到过兔子，我是说野兔，棕色的那种。

youdao

"My whole life,I'm like, I'm Mexican and I'm really -- I'm a proud Mexican-American and I swear I was an Aztec princess in my past life.

VOA: special.2010.09.13

And, I swear, it really contains Fresca.

我发誓，这里边装的真的是斯卡。

麻省理工公开课 - 固态化学导论课程节选

I, George Walker Bush, do solemnly swear... That I will faithfully execute the office of president of the United States...

VOA: special.2009.01.19

"I swear I had people offering to bake me cookies if they could get on the system, " he said.

WSJ: A Stathead Carves Out a New Market: High-School Coaches

And I could swear I saw an old bearded man wandering through the terminal chewing on an unlit Tyrolean gesteckpfeife.

FORBES: Interlude: Frankfurt International Airport and Feeble Attempts at German

"I'm sorry Batman, I swear I'll never do it again!"

WSJ: A Superheroic Caped Crusade to Keep Troops Safe in Afghanistan