SAMPLE with transparent background

I suggest creating one yourself with local tools...that will avoid "very questionable sites". Attached is one that I made by using Word 365, which has a built-in watermark doc with a diagonal SAMPLE (via the Design tab, then Watermark). I saved that as a PDF, then used GIMP to import the PDF and export it as a PNG with a transparent background. The file from that effort is attached. Regards, Joe

Edit: I didn't see Hello There's post until I hit the Submit button on mine. Clearly, he and I are on the same wavelength and his Photoshop suggestion is another example of a local tool that can do the job (I'm not familiar with the photopea.com site and can't comment on that).
SAMPLE-with-transparent-background.png

Considerations...

1) As @Joe suggested, many of these sites are... questionable... so if you only have 1x image, use Joe's attachment.

2) Keep in mind, overlaying a real image with transparent watermark image is fairly useless... because...

Usual reason to do this is to keep an image from being scrapped + used.

If you have your real image + watermark overlay, scrapping a copy of the real image is trivial, so you might as well skip the overlay.

3) The real way to do this depends on how many images + frequency of the task.

a) 1x image, likely you can find an online service to do this... keeping in mind @Joes comment...

b) If you have many images, use ImageMagick to automate the process...

https://legacy.imagemagick.org/discourse-server/viewtopic.php?t=33782 provides one of many discussions about the steps.

i used Windows Paint 3D to do this in about 5 minutes

make a transparent canvas
select Text
enter the text using the keyboard (SAMPLE)
rotate the text box using the curved arrow
save the image (.png selected automatically)

to do this in about 5 minutes

Same here for the Word/GIMP method. I knew that Word had a built-in diagonal SAMPLE watermark and decided to take advantage of that. But I just created the whole thing from scratch using only GIMP (attached), as you did with Paint 3D, and it also took just a few minutes (File>New>Fill with>Transparency, then the Text, Move, and Rotate tools, then Export As PNG). But your method has the advantage of using a built-in app instead of a third-party app...very nice! Regards, Joe

P.S. Seems that your comment posted twice. I'm marking only the first one as a Solution. :)
sample-via-gimp.png

thanks Joe
i edited the comment, seems to be a new bug in E-E

> i edited the comment, seems to be a new bug in E-E

Good to know!