This matchup may not be as easy as people think it is.
Ike has Jab that is quicker than ours (frame 3) and the first 2 hits can link into another Jab chain. Jab can knock you off the stage at high percents.
Ike has a sword. A giant one. With lots of priority, power, and range.
His tilts are all very powerful. F-Tilt may be one of Ike's more reliable kill moves. It's not fast, but it has awesome range. His Up-Tilt beat out everything we have from above, and has kill potential. I think this move may be fairly situational. Down-Tilt is situational, due to it's lack of speed and massive end lag. It has the ability to spike for an edgeguard as well.
All his smashes are powerful. F-Smash his extremely powerful with the ability to kill at around 60, maybe even lower. It has good range also. Down-Smash hits on both sides, but it isn't quick and is punishable. You won't see this move being used much if at all. Up-Smash swings in an arc, and hits in front, over, and behind him. It has a lot of range, and is hard to avoid when trying to land.
Ike will probably be approaching from the air. N-Air hits around him with very little landing lag. Ike can link this into a Jab, and N-Air (and all his other aerials,) have enough shield knockback (unless powershielded) to hit you out of range for a counterattack. F-Air is a commonly used approach. It has the most range out of any F-Air in the game. It hits hard and can KO when fresh. It also has either little landing lag or Interrupted as Soon as Frames upon landing (not sure which,) so punishing it's end lag (especially with a grab) isn't that easy. It aslo hits under him slightly. D-Air spikes when sweetspoted. When not sweetspoted it sends you into the air. B-Air is Ike's fastest aerial. It can be used in a shorthop with the move ending before landing. It comes out on frame 6 . Up-Air can kill and stays out for a while. This move can also be difficult to avoid from above.
His Neutral-B (Eruption) is one of the most powerful moves in the game when it's almost fully charged. It has deceptive range and Super Armor upon release I think. An uncharged Eruption can kill around 100. It has the ability to spike, but the massive end lag and the rare chances of it happening don't make the spike useful. His Side-B (Quick Draw) isn't save on the shield and is very punishable when it just misses the opponent. If he misses his opponent completely, he can do any action right after. Up-B (Aether) has Super Armor frames when Ike is on the way up. It hits multiple times and also spikes. Ike's Counter is one of the strongest counters in the game. It's pretty useless though, as it takes too long to activate, and missing a counter means extreme punishment.
Ike ***** Nana when the Ice Climbers get separated.
Ike can edgeguard us pretty easily. Every single move of his can hit us out of Squall Hammer (Jab included.) Reverse Aether Dragging will allow him to spike with Aether, while grabbing the ledge. He can use Down-Tilt to spike us if we are close to or hanging on the edge.
Ike has 2 recovery options. He can either Quick Draw, or use Aether. Most Ike users will almost never use Quick Draw. All it takes for them to fall is for you to get in the way of the attack. It also doesn't sweetspot the ledge, which can be a problem for them on some stages. They will use Aether to come back, usually at the lowest point possible so they can grab the edge and hit you at the same time.
If Ike grabs you, they will pummel to knock the other Climber away. Forward Throw is fast and will knock into the other Climber. Back throw may also be used, as it moves Ike in the direction he's throwing (away from you.)
Ice Blocks force Ike to approach due to his lack of projectile. Blizzard gives Ike problems, and Desynched Blizzards makes it difficult to approach. Squall Hammer racks up damage well on him also for damage and juggling him. Up-Airs should work well due to his weight and falling speed. He also has limited options when he's above us. You should be able to react to what he does when he's landing and punish accordingly. He's heavy, so chaingrabbing him shouldn't be that difficult.
Powershielding is extremely important if you want to grab/punish him. Most of his moves can be blocked on reaction, but if it's normal shielded the attack will knock you back too far to punish him.
Taking Ike to a stage with platforms like Battlefield may be a bad idea, as he can attack through the platforms easily. Delfino is a bad stage for use due to the water and platforms. Final Destination is the best stage to fight him on.
This is probably 6-4 in Ike's favor.