Considering I just installed it with no problems:
$ pamac install emacs Preparing...
==== AUTHENTICATING FOR org.manjaro.pamac.commit ====
Authentication is required to install, update, or remove packages
Authenticating as: Mirdarthos (mirdarthos)
Password:
==== AUTHENTICATION COMPLETE ====
Synchronizing package databases...
Resolving dependencies...
Checking inter-conflicts...
To install (4):
libotf 0.9.16-4 (Required By: emacs) extra 85.9 kB
m17n-db 1.8.0-4 (Required By: emacs) extra 1.5 MB
m17n-lib 1.8.0-13 (Required By: emacs) extra 327.2 kB
emacs 28.2-2 extra 42.6 MB
Total download size: 44.5 MB
Total installed size: 124.5 MB
Apply transaction ? [y/N] y
Download of m17n-db (1.8.0-4) started
Download of m17n-lib (1.8.0-13) started
Download of m17n-lib (1.8.0-13) finished
Download of emacs (28.2-2) started
Download of m17n-db (1.8.0-4) finished
Download of libotf (0.9.16-4) started
Download of libotf (0.9.16-4) finished
Download of emacs (28.2-2) finished
Checking keyring... [4/4]
Checking integrity... [4/4]
Loading packages files... [4/4]
Checking file conflicts... [4/4]
Checking available disk space... [4/4]
Installing libotf (0.9.16-4)... [1/4]
Installing m17n-db (1.8.0-4)... [2/4]
Installing m17n-lib (1.8.0-13)... [3/4]
Installing emacs (28.2-2)... [4/4]
Running post-transaction hooks...
Arming ConditionNeedsUpdate... [1/7]
Refreshing PackageKit... [2/7]
Updating icon theme caches... [3/7]
pacman-backup.hook [4/7]
Checking for .pacnew and .pacsave files... [5/7]
Updating the info directory file... [6/7]
Updating the desktop file MIME type cache... [7/7]
Transaction successfully finished.
I think your system and/or mirrors are of sync and not updated. So resync you mirrors:
sudo pacman-mirrors -f 5
And update your system:
pamac upgrade && pamac upgrade --aur --devel || echo -e '\033[0;91mThere was an error upgrading the system. AUR packages not upgraded.\e[0m'
Reboot, and try to install emacs again:
pamac install emacs
Hope this helps!
Tip:
When posting terminal output, copy the output and paste it here, wrapped in three (3) backticks, before AND after the pasted text. Like this:
```
pasted text
```
Or three (3) tilde signs, like this:
~~~
pasted text
~~~
This will just cause it to be rendered like this:
Sed
sollicitudin dolor
eget nisl elit id
condimentum
arcu erat varius
cursus sem quis eros.
Instead of like this:
Sed sollicitudin dolor eget nisl elit id condimentum arcu erat varius cursus sem quis eros.
Alternatively, paste the text you wish to format as terminal output, select all pasted text, and click the </> button on the taskbar. This will indent the whole pasted section with one TAB, causing it to render the same way as described above.
Thereby increasing legibility thus making it easier for those trying to provide assistance.
For more information, please see:

Additionally
If your language isn’t English, please prepend any and all terminal commands with LC_ALL=C
. For example:
LC_ALL=C bluetoothctl
This will just cause the terminal output to be in English, making it easier to understand and debug.