With one hand tied behind (one's) back informal
The word "hand" can be replaced by "arm".
Be able to perform something easily or effortlessly
Don't mess with me! You know I can take you down with one hand tied behind my back.
Don't worry! They're professionals. I'm sure they will get the job done with one hand tied behind their back.
Quickly and effortlessly
To win a competition easily
1. Something that is easy or effortless to achieve
2. Used to indicate the act of walking around while asleep
A simile to say that something is easy to do.
To indicate something that is very easy to do.
To say the same thing repeatedly
Ok, I get it! You sound like a broken record, seriously!