D tier
Lice and fleas are not exactly cute, badass or interesting looking. That's not bad on its own, however, the fact they actively drink human blood and carry potentially dangerous diseases makes them pretty bad. The one special skill either of these two have is that fleas have the largest jumps in the animal kingdom relative to their bodies. It's impressive ngl, but they still use it to bite people sadly. Flies aren't as directly harmful as the former two, but they're still pretty bad. They hang around garbage and contaminate any food they come in contact with (in large amounts ofc). They also make their signature buzzing sound, which can also get INCREDIBLY annoying. With that said, they're slightly better than lice and fleas since they don't go and drink people blood, but that's not saying much...
C tier
Cockroaches, much like flies, like hanging around in garbage and contaminate the food they come in contact with. However, what makes them escape D tier is the fact that a lot of species are actually not as harmful and can even be kept as pets, as well as their capacity of surviving impossible stuff, which at least makes them a lil more interesting. As for silverfish, bristletails and stoneflies, they're not particularly harmful in any way, but they rly aren't remarkable in any way. Guess that's the byproduct of being some of the most primitive insects.
B tier
Now we're getting into the better stuff! Wasps are pretty ferocious, with their bright coloring and buzzing being so infamous that many other insects mimic them in order to survive. Wasps can also be potent predators due to their painful stings and strong jaws. However, they're INCREDIBLY irritable, and their stings are no joke, so they stay in B. Mayflies are pretty cute looking, and they are some of the insects that spend their infancy in water formations before growing wings and leaving. However, mayflies have the one disadvantage of not having ANY mouthparts, so they have just one day to fly around, find a mate, make eggs with said mate and then die. It's kinda sad rly, so they land in B. Caddisflies are very similar, except they have more than a single day to enjoy their wings! The larval forms of some also make webs in which to shelter themselves in, which is pretty cool too! Ultimately they don't have much of other fancy stuff, so B seems fair enough.
A tier
Oooooh now comes the great stuff! Lacewings are pretty elegant looking, with their fragile build and large transparent wings. However, they also count with their more famous larval form, antlions! When they're like this, antlions create small funnels on the ground, that they'll then sit in the bottom of to wait and catch unfortunate insects that pass by. It's a pretty nifty tactic. Scorpionflies are actually not related to scorpions but they're still as epic! Scorpionflies have a pretty conspicuous stinger, which, believe it or not, is actually for mating purposes only, since they aren't capable of delivering poison with it. Still, they're pretty badass looking, and they also scavenge for dead insects, so they play a role in keeping the ecosystem healthy. Termites (third one from left to right is a worker while second one right to left is a juvenile queen) have an insane amount of coordination. They are pretty capable of making huge nests inside wood or dirt mound. They also feed on dead wood, which can be sorta annoying to humans and their houses, but ultimately help return the nutrients to the soil. Snakeflies are named as such due to their long necks that, individually, look like little snakes. Throughout all their lives they feed on pest insects that are harmful to plants. It's kinda sad, but ultimately it's for everyone's good....
Stick bugs are pretty conspicuous appearance mimicking an inanimate stick. They even have adapted to making the movements of sticks in the wind. Sadly they don't have much special things about them besides that, but it's still a very unique adaptation. Earwigs are also insanely recognizable, thanks to their forceps in their tails. These aren't for decoration either, since they actively use it for hunting, defending themselves and carrying prey to their burrow. Despite its menacing appearance, earwigs' forceps actually can't perforate human skin and aren't poisonous, so u can actually pick one up with the only harm being a slight pinch! (But preferably don't cuz it'll put great stress on the poor insect). Fairyflies are some of the most adorably small insects out there, with some only measuring 0.139 mm. They certainly are pretty cute, but they also have a parasitic side. Specifically, their larva parasitize other insects' eggs, specifically pest species. Much like snakeflies, they sadly have to eliminate other insects, but it's for the best of the whole ecosystem. Finally, web spinners are pretty badass looking. Much like their name implies, they spin webs to live in, sometimes in colonies! Despite that, they actually don't use them to hunt, and instead have a vegetarian lifestyle. They sadly don't have much defense aparts from the wings some of them have, so they depend a lot on their webs for protection.
S tier
Finally, la creme de la creme! Omega based insects! Dragonflies have practically never changed a bit in millions of years, and for good reason! They have binocular vision that allows them to precisely predict their prey's moves and act accordingly. They also have an also badass nymph form, that have an extendable jaw that they use to catch tadpoles, small fish and other water insects. Grasshoppers have the flea's talent of jumping insane distances, but without drinking blood! They are very drought resistant so it's not uncommon to find them in desertic regions. Some species have also developed spines on their legs, which they use for active hunting and self defense! Mantids are pretty much THE badass insect, to the point they inspired a Kung Fu style! Their hunting style is simple, camouflaging in the environment waiting for prey, and then grappling them with their arms to then eat them. There's a great variety of the colors and patterns they take, all depending on their hunting grounds (ones that hunt in leaves are green, ones that hunt in bark are brown and edgy, ones that hunt in flowers are colorful and with petal shapes, etc ). Now, an aspect they're famous for is that the female often eats the male's head after mating. However, this isn't entirely true. While they do that sometimes it's mostly when the female doesn't have enough nutrients to lay the eggs. If the female is well nutritioned tho, she'll leave the male alone. Butterflies are THE most colorful and varied insects out there. There's thousands of colorations and wing designs and shapes, making for an incredibly rich order. Their caterpillar forms are also incredibly varied, gaining varied adaptations for survival, like mimicry, poisonous spines, emitting irritating squeals, literally suplexing the offender and many many more. They sadly lose all those traits upon metamorphosis, but they compensate by becoming pollinators for diverse flowering plants, which is massively helpful. Beetles are also quite diverse, to the point most terrestrial living things are beetles! Despite that, they all share a similar body type, with their wings being covered by a hard shell. Their diet is also quite diverse, ranging from plant fluids, leaves, bark, roots and even other insects. They're kinda slow fliers, but their other attributes make this easy to overlook. Gladiator bugs are basically what u get when u cross a mantis and a stick bug. They're pretty active hunters, using their camouflage to close in on their prey before striking with their frontal legs. It's a neat little hunting style ngl. Barkflies, much like fairyflies, are adorably smol, with some only measuring 1 mm. Aparts from that they don't rly have much special, tho in this case I just think they're neat. Dobsonflies are absolutely terrifying, tho thankfully they don't want anything with humans. They have a similar life cycle to dragonflies, except they don't have nearly the same hunting efficiency as them. As a matter of fact, only larvae actually eat. Much like mayflies, once they reach adulthood they lose their mouthparts and die rather quickly (tho not as fast as mayflies). As larvae they feed on larvae of other insects, including dragonflies. Like fairyflies, u just think they're neat! Finally, true bugs, the irl bug types! They have many adaptations for diverse situations. Their diets are diverse, ranging wide between sap, fruit and other insects. Some of them also count with heavy chemical defense, which they utilize when they feel threatened, while others can inject poison through their proboscis. Overall, quite the rainbow of an order.