--->Web Spider- The X buster works fine, you should go after him first.
--->Split Mushroom- After you defeat Web Spider, go to Split Mushroom's stage and use the Lightning Web to take him out quickly and easily.
--->Cyber Peacock- After getting Soul Body from Split, use it on Cyber Peacock to win with no questions asked.
--->Storm Owl- Use Cyber Peacock's Aiming Laser to take down Storm Owl in seconds.(well it seems like seconds at least)
--->Magma Dragoon- Use Storm Owl's weapon to beat Magma Dragoon no sweat.
--->Frost Walrus- Fire beats ice. Who saw that coming??
--->Jet Stingray- Use Frost Tower, but he is still kind of tough.
--->Slash Beast- Use the Ground Hunter to promptly kick his butt.
*Note- Slash Beast's Twin Slasher works well on Web Spider.
If you follow this pattern, you should be at the Spaceport and then you will fight Colonel again.
--->Colonel- Just use the X-Buster!!!
--->Sigma first form- Use Rising Fire, and you will find him to be quite easy.
--->Sigma second form- Not so easy. Use Lightning Web to make it a lot easier.
--->Sigma 3rd and 4th forms- Whoa. VERY VERY HARD. The 3rd and 4th forms attack alternately. This is the pattern- The Heads, The Old Man Face, The Heads, Giant Robot. For the heads, avoid their attacks and shoot them with anything. When The old man face comes up, Use Ground Hunter and dash when the tornadoes come up, and hide behind the blue head and use the X-Buster when he shoots rocks at you. The Giant Robot is fairly simple. Just Wall jump on the heads, charge up, then shoot him in the head. Repeat this pattern to win!!
--->***Also- When you get the Enhanced X-Buster that charges up 4 shots, go left to find another capsule containing Plasma Shot. THIS MAKES THE 3RD AND 4TH FORMS MUCH EASIER.You can still get the charge-up shot if you want, but the Plasma Shot makes it 20 times easier in my opinion.