Retrieve Position of last Character of Textlayer

Any solution for this will be a bit of a hack as there's no in built method for it.

You may be able to get somewhere using the AV Layer sourceRectAtTime() method. I've used this approach in the past. It won't work so well if the text layer contains multiple text styles though.

Basically, you find the extents [top, left, width, height] of the whole text layer, then temporarily change it to just the last character (or use a dupe of the layer) and find the new extents. From this you can accurately work out the left and right values.

i.e. right = (fullExtents.left + fullExtents.width);

left = right - lastExtents.width;

Top and bottom is a bit tricker as the last character height might not match the full layers height because of ascenders/descenders, so you may also need to do things like test the extents with examples of each to figure it out.

Another possible solution is to use the sampleImage() expression, applied by a script that also reads the resulting values, after applying a text animator to set Opacity to 0% on all but the last character. It can be slow and laborious but you could sample multiple pixels (preferably using well optimised logic to minimize the number of samples required) until you find the bounds from the pixel alpha values.