Komplete includes a lot of samples, but it also includes several great synths and some effects.
- FM8 is a six-operator FM synth with arbitrary routings (including feedback) for all operators. Much more powerful than Operator, but also more complicated to get your head around.
- Massive and Absynth are powerful subtractive synths that go well beyond what Analog can do.
- Reaktor is what got me into Komplete in the first place. It is a highly flexible modular environment with a great library of synths and FX. Reaktor alone is worth the price of admission, though FM8, Massive and Absynth are faster to work with when they do what you need.
- Guitar Rig is a box of guitar pedal simulators. Great for quickly trying out FX. Despite the name, Guitar Rig is GREAT for use with synths.
That said, you can do a lot with the synths and FX included in Live. If you aren't sure why you need Komplete (or, anything, really) then don't buy it until you do. NI tends to release new versions of Komplete frequently, so it is possible that K9 is just around the corner.