It is essential that you find out straightaway what species your tigerfish is.
I've done a quick Google, but all the Asian tiger fish I can find are a) brackish B) need very large tanks. Hopefully, you haven't got one of those, but you really must know what your fish is in order to be able to cater to its needs. Let us know what you've got.
The barracuda, as stated above, will grow too large for the tank. The stunting of growth in fish can work in different ways, depending on species, either they stay small (and unhealthy), or they get say a deformed tail (if unable to move properly), or they simply die before their time, or they become irritable and/or susceptible to disease. In a small tank like yours the most likely outcome is that it will die from ammonia poisoning before it has the time to develop the other problems.
The fact that you have seen one 8 inch fish of this species tells us nothing about how big they can grow or how big they need to grow if healthy.
A 10 gallon tank is suitable for small fish such as minnows, guppies, small rasboras, one betta, one dwarf puffer (if you have the facilites and expertise to look after it properly), African dwarf frogs, platies, small corydoras etc.
To keep Oddballs, you need a good-sized cycled tank and, usually, very good filtration. For most people it works better to start with something hardier and work their way up. That way you will learn about cycling a tank, keeping the water stats stable etc before you try your knowledge out on something really sensitive (and expensive).