These are the first eight original bosses of Megaman X.
 Armored Armadillo
Armadillo is very basic in his attack patterns. He'll simply curl up and smash about all over the place. Due to his armor, scoring hits is extremely difficult which is why using the Electric Spark is advisable.
With his armor removed, Armadillo will start using the blaster hidden in his head to launch a steady stream of bullets at X. Electric Spark can still easily interrupt him but remember that he now lacks defensive abilities.
 Boomer Kuwanger
This boss is difficult but a sub-tank or the Homing Torpedos should suffice.
To start off, Kuwanger has the ability to teleport. Where he'll re-appear is always random but limited to the ground. Be warned that if he does appear next to X, he will hurl him into the ceiling.
Clinging to the walls is a good strategy here but with Kuwanger's dashing and boomerang he can often be waiting right beneath X and knock him down with a Boomerang Cutter.
If using the X Buster, it takes quick movement and a sharp eye to take this guy down. Homing Torpedos just require staying on the wall and firing away.
 Chill Penguin
Though extremely easy to beat, Chill Penguin has a range of attacks.
He'll typically start by sliding around the stage. Simply dodge this by jumping up the walls, take note that he can ricochet off the walls a bit.
He can also jump upwards to pull the switch on the ceiling trigger a snowstorm that pushes X to the wall. This can be stopped by knocking Penguin back down with a charged X-Buster shot.
Chill Penguin also has the ability to create ice penguins which the blizzard can also push though he'll often break them by sliding through them.
Additionally he can use Shotgun Ice, which allows him to pelt out bullets of ice.
His attacks are slow and often predictable so just nail with charged shots when possible and stick to the walls otherwise.
 Flame Mammoth
This giant reploid makes use of his weight and his moving arena.
The first thing to note is his mega jump, not only is it slightly difficult to avoid due to his side but his landing will stun X momentarily which is always an annoyance. He'll occasionally spit out tar and later spit out fireballs ahead of him in a 90 degree arc. If the flame hits the tar it creates a temporary fire tower. Though not entirely useful, he can also change direction of the treadmill ground of the arena.
Storm Tornado makes him extremely easy as it knocks him out of his jump however the X buster can suffice.
 Launch Octopus
Launch might look menacing but he actually isn't that bad. Taking him down with the X Buster is feasible if you've either expanded your health to a good degree or are carrying a sub-tank or two.
For starters, Launch will launch barrages of torpedos in groups of three. If you stay on the ground and fire straight ahead with normal shots you should protect yourself from any damage. Though you can, do not cling to the wall as you'll set your self up to get hit with his E. Drain attack.
He can also jump and fire a second barrage of torpedos but that isn't of great importance as you'll probably spend most of the fight on the ground.
Occasionally he'll launch four homing torpedoes which can be evaded by moving around at such a high speed that the torpedoes can't turn fast enough to hit you. They can turn rapidly so using the wall to kick off of is a good idea though he'll usually launch this when he's jumping over you leaving a dash all that's needed to evade.
His final move he abuses a lot (unsuccessfully). He'll jump high up and form a current around himself that extends above and below. This draws X to in but can be dodge by dashing. If he does catch you in this, he'll latch onto X and drain energy. This damages X and heals him. However, since the move is easy to dodge, all you need to do is charge up and wait for him to land to send a blast home.
Rolling Shield is more effective and the strategy works in the same manner.
 Spark Mandrill
Spark Mandrill isn't difficult if you know how he functions. He may look like he's slow but he compensates with high attack speed.
Mandrill will start the fight by either jumping towards X or swinging from the wires at the top of the room. To make him drop simply run under him and he'll try to land on X though this is easy enough to avoid.
However once grounded, he'll start unleashing attacks rapidly so get ready to bounce off the wall with dash jumps. He'll either punch the ground to send electric sparks around the wall which is easy enough to avoid or he'll Dash Punch into the wall with enough impact to knock X down the wall. You're best off bounding to the wall and bounding off as fast as possible despite not knowing what attack is coming.
Shotgun Ice renders a strategy useless. Just pummel him with shotgun which will also freeze him. Aiming is not needed to the bouncing off walls effect of the weapon.
 Sting Chameleon
This Maverick is tough, it is highly recommended that you only fight him with the Boomerang Cutters.
For starters, Sting Chameleon can move around while invisible making hitting extremely difficult. He can also use this to sneak up on X and quickly lash him with his tongue and disappear.
He'll also head to the top of the arena and latch onto it with his tongue and shake the roof causing spikes to hail down (non-lethal). He can be knocked down from this with a well placed Boomerang Cutter.
When higher up, he will occasionally flick a Chameleon Sting at X with his tail, since these come in bursts of 3 they are not completely easy to avoid.
 Storm Eagle
The easiest Maverick to defeat attack wise, Storm Eagle is typically number two on the list as you simply cannot beat him without the Foot Upgrade from Chill Penguin's stage.
The battle ground for this level is wide and has no walls so staying in the middle is advisable. Storm Eagle will start by creating a gust with his wings. This is why you need the boots as you need to dash so that you aren't pushed over the edge.
He'll eventually use Storm Tornado which simply pushes you faster if you touch it so try to long jump as much of it as possible.
His main attack is Eagle Diving. He'll fly off stage and you won't see him for a while. Get ready to dash as he'll dive down toward X. If you're fast enough, you can land a shot on him but don't worry about it if you can't.
His last attack is spitting an egg that produces four Eaglets, each can be destroyed with the X Buster. He also lingers for a moment so get some damage in.
Chameleon Sting is his weakness but the X Buster can handle him easily.