The sticky bomb launcher is fundamentally the most unbalanced weapon in all of tf2. Although items such as the phlog, scorch shot, or the sniper rifle are unbalanced and are frustrating to play against nothing quite competes with the Sticky bombs. This is because of the sheer versatility and power of the stickies. Most weapons have counter play that if played correctly any class will be able to either completely avoid, such as the sniper rifle, or have direct counters, such as rockets with the phlog. The sticky bomb launcher has neither of these. Furthermore some weapons are specifically made to counter other classes. Demo counters all classes with the exception of sniper just because snip[er should never be near the frontlines with the exception of huntsman sniper, which demo does counter. This is because of the offensive and defensive capabilities of the stickies. On offense the stickies are specifically made to destroy sentry nests. While this isn't a problem, his stickies do so much damage that he can simply spam them to destroy any defense. While some may argue that solider has the exact same capabilities, this isn't true because solider has a direct counter in pyro's airblasts which forces a solider to be smart about rocket placement or face a lethal reflect. However with demo the sticky bombs can be reflected to deal insignificant damage. This is because the stickies would need to be reflected in mid air directly at the demo, and for the demo to be braindead enough to still detonate the stickies in his face. Some teams build ubers in order to destroy sentry nests, which is balanced because it requires not only someone to play medic, but to heal people for long enough to actually use the uber. Meanwhile a demo can mindnumbingly walk forward place a couple stickies and totally destroy a sentry nests. Once thats been done he can move on to spamming it at every class he faces in order to easily kill any class including heavy. On defense his power is even more egregious. This is because demo is able to spam down choke points which he knows enemies will be. This encourages terrible gameplay. The very worst case scenerio for a demo man is that he has to retreat in which case he will be able to lay traps behind door frames that have the potential to instantly kill any class. If this doesn't work he can switch to a primary that can deal 100 damage. While pills are balanced because of the ability to reflect them and also the difficulty to land pills; pairing two of the most damaging weapons together cause for a huge imbalance in the game.
Altogether spy is a terrible class and anybody that plays him needs to touch grass<3.