Can anyone help me I keep killing RegiRock,RegIce,rayquaza and Latios or..

If you get the egg from the 4th gym leader city, hatch that and it will be a wyatt, it's ability is shadow tag which is that wild Pokemon can't run away from it, keep it at the level 15ish or so, you have a more likely chance of running into latios if you have a lower level Pokemon and it needs some power behind it to take on wild Pokemon and to survive an attack possibly, if latios is already down then it's your chance to throw some poke balls, if not already down in hp then you probably don't want to do this because it doesnt have any real attacks other than counter like attacks, the other Pokemon though, I would get an electric type Pokemon and get it to about 45ish for the Regi's, have it know thunder wave, thunder wave will hit all three, yes one is rock but it's not part ground so it will work, then just keep taking them down to the red and start throwing some ultra balls, if you bring 50, and some revives and stuff so your party doesnt die, your gaureented to get them if they are paralyzed and in the red. Rayquaza the same but train the electirc guy to at least 65ish, electirc are usually quick attackers so just use it to paralyze him, good luck, sorry the latios one doesnt really help and that this is pretty long, haha

Use weak attacks and ake it at the red zone, then make it paralyze or fall asllep and then start throwing the balls!!

Use weak attacks and paralyze it, sleep it and then try to catch it.