How to Remove / Hide "Powered by Blogger" (Attribution Gadget)

Settings -> Template -> Edit HTML

Method 1:
add the following before </head>:
<style>#Attribution1{display: none;}</style>

Method 2:
 -> Jump to widget: choose Attribution1

Change it to:

<b:widget id='Attribution1' locked='false' mobile='no' title='' type='Attribution'/>

Go to Layout, remove Attribution1 widget.

To hide: Template -> Customize ->  Advanced -> Add CSS - Paste the following code  -> Apply to Blog:

#Attribution1 {
display: none !important;
}