Malcat is described as 'feature-rich hexadecimal editor / disassembler / decompiler for reverse engineers and malware analysts. It has support for many file formats and CPUs, can scan for signatures, decrypt/decompress data, diff files and run python scripts' and is an app in the Development category. There are more than 10 alternatives to Malcat for a variety of platforms, including Windows, Linux, Mac, FreeBSD and BSD. The best alternative is IDA. It's not free, so if you're looking for a free alternative, you could try Ghidra or radare2. Other great apps like Malcat are 010 Editor (Paid), Cutter (Free, Open Source), Binary Ninja (Paid) and Ghex (Free, Open Source).
010 Editor is a professional text/hex editor designed to edit any file, drive, or process on your machine. Using Binary Templates technology, 010 Editor allows a binary file to be parsed into a data structure that can be understood.
Radare project started as a forensics tool, a scriptable commandline hexadecimal editor able to open disk files, but later support for analyzing binaries, disassembling code, debugging programs, attaching to remote gdb servers, ...
GHex - a hex editor for GNOME GHex allows the user to load data from any file, view and edit it in either hex or ascii. Useful for debugging problems with object code or encodings. Also used by kids who cheat at computer games, by adding score or lives to saved games