Hi Shaiq,
Audio power amplifiers use usually complementary power transistors operating as emitter-followers at their output to provide enough current and symmetry.
DC negative feedback is used to provide a stable DC operating voltage and AC negative feedback is used to create a certain voltage gain, low distortion and wide bandwidth.
I don't think a single transistor can drive an 8 ohm speaker properly unless a transformer is used to couple it to the speaker. If a single transistor/transformer power amplifier is made, with a power output rating of only a few watts or more then the transistor will get very hot even without an output.