Hello,

for particular item approval, when user receives an email, can email contain button of approve/reject or if user just replies to that mail using one word "Approve/Reject", so that item value should get updated in list and also get approved.

Is it possible using SharePoint designer workflow or custom code workflow or Nintex workflow?

Please guide.

Thanking you in advance.

Regards,

Jayashri

Follow these steps:
You can create custom page with code to approve/reject item.
Then you should pass item id (and other information if needed) in a query string.
In a workflow you can generate a link to the created page and add it to email body.

When a user will receive email, he/she will click on the button (link), then new tab with created page will be opened, where your custom code will approve an item.