which bond is strongest? 
and arrange the following in decreasing order

• ionic bond
• co ordinate bond
• covalent bond
• hydrogen bond

The strength of the bond is
Ionic bond > Coordinate bond > covalent bond > hydrogen bond.
The reason is ionic bond is formed by electrostatic force of attraction between the two atoms and covalent bond is formed by the same electronegative atom. Coordinate bonds are having intermediate strength between the two and hydrogen bond is a special type of vander Waal's force of attraction.