I tried to flash stock via update firmware page and it is now stuck in bootloop.
If you cannot make it tftp you need a serial cable.
Not according to this guy: Bricked TP-Link WR841N/ND Recovery Unbrick Without A Serial Connection - YouTube
Also this thread mentions it being done without a Serial Connection: https://community.tp-link.com/en/home/forum/topic/218064
Maybe it only works on older units? 
Check with tcpdump, for any tftp or serial to work you need OEM bootloader in place.
Fo some you need to add arp -s 192.168.0.1 MAC-OF-ROUTER-LABEL on the tftp server.
Could be the OEM bootloader is the problem as I am not sure exactly which OEM bootloader will work with this Colombian model.
Device was:
128k OEM bootloader
openwrt kernel ~5M
openwrt squashfs ~ 1M
openwrt rootfs_data ~1.5M
64k caldata
---- 8MB flash ends
You forced second bootloader where the active bootloader expects kernel. So what first bootloader does is all you got.
This is what it was running:
So basically what you are saying is that without the serial cable connection it is trashed and should be put into the electronics recycling bin.
Yes, it is like that.
And if first bootloader is damaged you will need flash programmer, so yes, lets not waste 50 bucks to fix 10 bucks device (and read manuals more carefully next time)