I found that with about 6 Orca Bombers the Defender goes down pretty easily. It walks so slowly that you have time for at least 4 runs with them, plenty to destroy it. If you're getting freaked out about it then just send everything you have to slow him down but it will end up with all your ground forces getting wiped out. If you want to be on the safe side then make more bombers and blow the crap out of it.
This tip is for the last mission. If you are NOD, then you will need a GDI war factory in order to do the following.
If you are GDI, build 50 disrupters, and rush them to take out Cabal Core. Their beam can penetrate the
firestorm walls. So is Devil tongue(but the range is
shorter). This can allow you to skip the objective of capturing the 3 Civilian Arrays shown on the radar. Might be challenging for you to create such a big amount of disruptors. So if you have a trainer, just use it.
If you are playing as GDI on the final mission this is the exteremly easy way of beating Core Defender. At the base North of your base capture it's buildings and construct a GDI construction vechile and place at what's left of that base. A little bit North of your base there is a cliff build silos and placxe them near the Tiberium Regentration plant thing. But they have to be near the cliff. next make sure that you put things in a line leading to the bottom of the cliff. If you did it right the Defender will destroy every that you put in a line and will try to destroy your silos but it cannot. It might deestroy at lest two of them and then you can use any thing against it. Before you get to the part where he activates the Defender take over the Nod bases even the one close to the Core and up it's defences by building walls and any thing that can slow the Defender down At least 7 wall layers. To get that much mony you have to first find and capture the silos and Miner depsoites.(Hint caputer the Miner deposites when the miners is ther dropping its load. You get the building and the miner that way!) It took me only 45 minutes to beat the final level! And I had over 230000 in tiberuim and one massive army at least of 2000! With only 7 miners.
Since the Core Defenders are very hard to defeat, then follow this steps.
If you are GDI
1. Capture a NOD Construction Yard
2. Cloak your base and troops with Stealth Generators
3. Have 1 infantry attack ground(press Ctrl and click on the ground)
4. Build firestorm wall sections around the infantry, the wall sections must be CLOAKED!
5. When CABAL released the Core Defender, the Core Defender will definitely go to that infantry who is uncloaked, so lure the Core Defender into the firestorm wall sections.
6. Once the Core Defender step onto your firestorm wall section, have the firestorm generator activated, it will smash that machine into a junk!
If you are NOD:
You do not need a GDI Construction Yard for this
Same steps actually, but u replace the words "firestorm wall sections" with "laser fence sections". After you build the laser fence section, use the power mode to deactivate them, when you have lure the Core Defender into the laser fence section, have the Power Mode ready on your mouse, and activate the laser fence section once it steps on it!