I want light controlled by one switch, not two
This is what happens when you randomly tear stuff off the wall without taking pix first.  I'm guessing you assume the wire colors are meaningful in some way; colors mean less than than you think, and less than nothing at all in 3-way circuits. That stinks, so get some yellow electrical tape; we need to make colors meaningful. 

Looking at the 3-way switch still wired, it appears a black wire is on the black screw (coincidentally).  That means the two brass screws are red and white -- those are travelers and mark them both yellow with tape.  

On 3-way switches, travelers go to brass screws. That's what you must remember.  Switch manufacturers randomize the location of black and brass screws on every model of switch. 

The other switch, we don't know.  However, 90% of the same time, the travelers here are simply the other end of the same cable, so they'll be the same colors -- red and white in this case.  

That's tricky because  there are two reds, but hold on, didja catch that? The travelers are in the same cable.   So follow the white wire back, see which red wire joins it in the same cable, and voila - those two are your travelers.  Mark them yellow. 

Whoo! We now have the 2 travelers identified.  Now everything gets easy. 

There were 3 wires (besides ground) going to the old switch. Pick one traveler at random and cap it off. You will need tape to hold a wire nut on a single wire.  Join the remaining two wires with a wire nut, but don't tape it - if it won't hold by itself, it's a bad connection and it will arc and start a fire. 

At that point, the switch will work in one position.  If it works in the "down" position, flip the switch over when you install it. 

A few more matters

You may notice you can go into 99% of rooms and find the light switch immediately.  That works because the Building Codes require you have switches in certain locations.  You are not allowed to have "secret switches" that only you know how to turn on. This protects both your invited guests and first responders: so the EMT can see to save your life, and the cop can see that's a computer mouse not a gun in your son's hand. 
Make sure that your switch removal does not violate the building codes or make it hard (for visitors) to get a light switched on in that room. 

Also, I must warn you that you cannot bury electrical junction boxes. You currently have a blank cover there; that must stay there forever until you run a new cable which bypasses this box, and remove those cables.  Further, you may want to leave it as a house feature, in case the new owner wants to restore that switch.  (or the pre-sale inspection reveals the switch is mandatory).